JPWO2014081046A1 - Image forming apparatus and electrophotographic photosensitive member - Google Patents

Abstract

In an image forming apparatus that forms an electrostatic image on an electrophotographic photosensitive member using at least a pseudo halftone process formed of dots as a technique for expressing gradation, the surface of the electrophotographic photosensitive member has a depth of 0.5 μm. A plurality of recesses having an opening of 5 μm or less and a longest diameter of 20 μm or more and 80 μm or less are formed. When a square region having a side of 500 μm is extracted on the surface of the electrophotographic photosensitive member, the area of the recess in the square region is 10000 μm 2 to 90000 μm 2, the area of the flat portion included in the portion other than the recess is 80000 μm 2 to 240000 μm 2, and the arrangement of the plurality of recesses (A) is calculated by performing a specific calculation process (f) ) Is 14% or less.

Description

  The present invention relates to an image forming apparatus and an electrophotographic photosensitive member.

Since an electric external force such as charging or cleaning or a mechanical external force is applied to the surface of the electrophotographic photosensitive member, durability against such external force (such as wear resistance) is required.
In response to this requirement, conventionally, improved techniques such as using a highly wear-resistant resin for the surface layer of the electrophotographic photosensitive member have been used.
On the other hand, a problem caused by increasing the wear resistance of the surface of the electrophotographic photosensitive member is image flow. In the image flow, the material used for the surface layer of the electrophotographic photosensitive member deteriorates due to an oxidizing gas such as ozone or nitrogen oxide generated by charging of the surface of the electrophotographic photosensitive member, or electrophotography occurs due to moisture adsorption. This is considered to be caused by the fact that the surface of the photoreceptor is lowered in resistance. The higher the abrasion resistance of the surface of the electrophotographic photosensitive member, the more difficult the surface of the electrophotographic photosensitive member is refreshed (removal of materials that cause image flow such as deteriorated materials and adsorbed moisture), resulting in image flow. It becomes easy to do.
As a technique for improving image flow, WO05 / 093518 (International Publication Number) discloses a technique for providing dimple-shaped concave portions on the surface of an electrophotographic photosensitive member by dry blasting or wet honing. According to WO05 / 093518 (International Publication Number), a plurality of dimple-shaped recesses are provided on the surface of an electrophotographic photosensitive member, whereby image flow from the initial stage to about 5000 sheets can be suppressed.
Japanese Patent Application Laid-Open No. 2007-233355 provides good dot reproducibility from the initial stage to about 50000 sheets even in a high temperature and high humidity environment by providing a plurality of concave portions on the surface of the electrophotographic photosensitive member at a high area ratio. A technique for maintaining, i.e., suppressing image flow is disclosed.
Japanese Patent Application Laid-Open No. 2011-22578 discloses a technique for providing concave portions on the surface of an electrophotographic photosensitive member with a low area ratio.
As described above, a technique for providing a plurality of recesses on the surface of an electrophotographic photosensitive member has been studied as a technique for suppressing image flow. In designing a plurality of recesses, items such as the surface roughness, the size of each recess, or the number of recesses in a certain area are attracting attention.
On the other hand, there is an item “arrangement of recesses” as a design item for a plurality of recesses. Conventionally, the density of the recesses has been studied, but no attention has been paid to how the recesses are arranged.
As a technique paying attention to the arrangement of the recesses, Japanese Patent Application Laid-Open No. 2007-233359 discloses a technique for suppressing the growth of scratches by arranging the recesses within 50 μm in the rotation direction of the electrophotographic photosensitive member.

The present invention is a further development of the above prior art. That is, an object of the present invention is to provide an image forming apparatus and an electrophotographic photosensitive member that are less likely to cause image flow and that can suppress deterioration in image quality due to a concave portion on the surface of the electrophotographic photosensitive member.
According to the present invention, an electrophotographic photosensitive member comprising at least a support and a photosensitive layer formed on the support;
An image forming unit that forms an electrostatic latent image on the electrophotographic photosensitive member using at least a pseudo halftone process formed by dots as a method of expressing gradation,
A plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less are formed on the surface of the electrophotographic photoreceptor,
When one side in the surface of the electrophotographic photoconductor were arbitrarily extracted square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the flat portion contained in a portion other than the recess The total area is 80000 μm ² or more and 240000 μm ² or less,
The image forming apparatus, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.
<Calculation processing>
(1) From the screen pattern (B) generated by the pseudo halftone process formed by dots, the portion overlapping with the plurality of recesses is deleted to obtain an image (C). (2) Particles for the image (C) Analysis is performed, and the dot area average value SM and the dot area standard deviation (σ) are calculated. (3) The image quality degradation index (f) is obtained by the following equation (1).
Is provided.
Further, according to the present invention, an electrophotographic photosensitive member comprising at least a support and a photosensitive layer formed on the support;
As a technique for expressing gradation, an image forming unit that forms an electrostatic latent image on the electrophotographic photosensitive member using at least a pseudo halftone process formed by dots, and cleaning by contacting the electrophotographic photosensitive member An image forming apparatus having a blade,
A plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less are formed in at least a contact region with the blade on the surface of the electrophotographic photosensitive member,
When one side in the contact region is arbitrarily extract a square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the total area of the flat portion contained in a portion other than the recess 80000μm ² or more and 240,000 μm ² or less,
The image forming apparatus, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.
<Calculation processing>
(1) From the screen pattern (B) generated by the pseudo halftone process formed by dots, the portion overlapping with the plurality of recesses is deleted to obtain an image (C). (2) Particles for the image (C) Analysis is performed, and the dot area average value SM and the dot area standard deviation (σ) are calculated. (3) The image quality degradation index (f) is obtained by the following equation (1).
Is provided.
Furthermore, according to the present invention, there is provided an electrophotographic photosensitive member on which an electrostatic latent image is formed using at least a pseudo halftone process formed by dots as a technique for expressing gradation,
A support, and a photosensitive layer formed on the support,
On the surface of the electrophotographic photosensitive member, a plurality of recesses having a depth of 0.5 μm to 5 μm and a longest diameter of the opening of 20 μm to 80 μm are formed,
When one side in the surface of the electrophotographic photoconductor were arbitrarily extracted square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the flat portion contained in a portion other than the recess The total area is 80000 μm ² or more and 240000 μm ² or less,
The electrophotographic photoreceptor, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.
<Calculation processing>
(1) From the screen pattern (B) generated by the pseudo halftone process formed by dots, the portion overlapping with the plurality of recesses is deleted to obtain an image (C). (2) Particles for the image (C) Analysis is performed, and the dot area average value SM and the dot area standard deviation (σ) are calculated. (3) The image quality degradation index (f) is obtained by the following equation (1).
Is provided.
Furthermore, according to the present invention, an electrophotographic photosensitive member in which an electrostatic latent image is formed using at least a pseudo halftone process formed of dots as a technique for expressing gradation and the surface is cleaned by a blade. Because
A support, and a photosensitive layer formed on the support,
A plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less are formed in a contact area with the blade on the surface of the electrophotographic photoreceptor.
When one side in the contact region is arbitrarily extract a square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the total area of the flat portion contained in a portion other than the recess 80000μm ² or more and 240,000 μm ² or less,
The electrophotographic photoreceptor, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.
<Calculation processing>
(1) From the screen pattern (B) generated by the pseudo halftone process formed by dots, the portion overlapping with the plurality of recesses is deleted to obtain an image (C). (2) Particles for the image (C) Analysis is performed, and the dot area average value SM and the dot area standard deviation (σ) are calculated. (3) The image quality degradation index (f) is obtained by the following equation (1).
Is provided.

In FIG. 1, (A) and (B) are diagrams schematically showing a relationship between a reference surface, a flat portion, a concave portion, and the like.
2A to 2G are diagrams showing examples of the shape of the opening of the concave portion on the surface of the electrophotographic photosensitive member.
3A to 3G are diagrams showing examples of the cross-sectional shape of the recesses on the surface of the electrophotographic photosensitive member.
FIG. 4 is a view showing an example of a press-contact shape transfer processing apparatus for forming a concave portion on the surface of the electrophotographic photosensitive member.
FIG. 5 is a diagram showing an example of an electrophotographic apparatus.
6A to 6D are views showing a mold used in an example of manufacturing an electrophotographic photosensitive member.
FIG. 7 is a diagram showing an example of fitting.
FIG. 8 is a view showing the result of cross-sectional observation in the vicinity of the surface layer of the electrophotographic photosensitive member.
FIG. 9 shows an example of a dry blasting apparatus.
FIG. 10 is a diagram for explaining a narrow portion.
In FIG. 11, (a) is an enlarged view of an example of a screen used in pseudo halftone processing, and (b) is a recess arrangement in which recesses close to the dot size of the screen pattern having an aperture diameter (a) are irregularly arranged. The figure which showed an example, (c) is the figure which showed an example of the recessed part arrangement | positioning which arrange | positioned the recessed part which the opening diameter is extremely smaller than the dot size of the screen pattern of (a) irregularly, (d) is the figure of (b) The figure which assumed the output image at the time of outputting the screen image of (a) using the electrophotographic photosensitive member by which the recessed part arrangement | positioning was made, (e) is using the electrophotographic photosensitive member by which the recessed part arrangement | positioning of (c) was made. FIG. 5A is a diagram assuming an output image when the screen image of FIG. 5A is output, FIG. 5F is a diagram in which (d) is reduced and (g) is a diagram in which (e) is reduced.
12A is an enlarged view of a screen having an angle of 45 ° when the main scanning direction of exposure light is set to 0 °, and FIG. 12B is an enlarged view of a screen having an angle of 45 ° when the main scanning direction of exposure light is set to 0 °. (C) is an example of a square arrangement, and an example of a concave arrangement with an angle of 26.6 ° when the main scanning direction of exposure light is 0 °. The figure shown, (d) is a figure assuming an output image when the screen image of (a) is output using the electrophotographic photosensitive member having the concave portion arrangement of (b), and (e) is the figure of (c). It is the figure which assumed the output image at the time of outputting the screen image of (a) using the electrophotographic photoreceptor in which the recessed part arrangement | positioning was made.
FIG. 13 is a graph showing an example of a VTF function (visual spatial frequency characteristic).
14A is a diagram showing an algorithm of the Floyd-Steinberg method, and FIG. 14B is a diagram showing an example of an irregular pattern generated by the Floyd-Steinberg method.
15A is a view showing an example of a mask used in a method for forming a recess by laser light irradiation, and FIG. 15B is a view showing an example of a recess forming apparatus by laser light irradiation.
FIG. 16 is a diagram illustrating a dot-concentrated dither matrix of 1200 dpi, 106 lpi, and 45 degrees.
FIG. 17 is a view showing an example of a photograph of the surface of the electrophotographic photosensitive member having a recess, obtained by GX-700.

The feature of this example is that it combines the following four items.
Feature 1: The longest diameter (major axis diameter) of the opening of the recess is large
Feature 2: The ratio of the area of the recess is small
Feature 3: Large proportion of flat area
Feature 4: The recesses are arranged to meet specific criteria
Features 1 to 3 are items for suppressing image flow, and feature 4 is an item for suppressing deterioration in image quality. Details will be described below.
<Suppression of image flow>
First, features 1 to 3 that are items for suppressing image flow will be described. In the features 1 to 3 of this example, the feature of the technique described in the above-mentioned WO 05/093518 (International Publication Number) is that the ratio of the area of the flat portion on the surface of the electrophotographic photosensitive member is large. When a dimple-shaped recess is provided on the surface of the electrophotographic photosensitive member using dry blasting or wet honing, particles are allowed to randomly collide with the surface of the electrophotographic photosensitive member. Of these, the ratio of the area of the flat portion is extremely small.
In addition, regarding the features described in Japanese Patent Application Laid-Open No. 2011-22578 in the features 1 to 3 of this example, the surface on the surface of the electrophotographic photosensitive member is flat as in the case of the features of WO05 / 093518 (International Publication Number). The ratio of the area of the part is large.
In addition, in the features 1 to 3 of this example, the feature described in the above-mentioned Japanese Patent Application Laid-Open No. 2007-233355 and Japanese Patent Application Laid-Open No. 2007-233359 is that the concave portion having a large longest diameter (major axis diameter) is an electron The point provided on the surface of the photographic photosensitive member and the area ratio of the recesses are small.
In this example, the area of the recess means that the surface of the electrophotographic photoreceptor is substantially parallel to the normal direction perpendicular to the surface of the photoreceptor (the radial direction in the case of a cylindrical photoreceptor) from above. It is the area of the recess when it is, and means the area of the opening of the recess. The same applies to flat portions and convex portions.
The results of the study by the present inventors were as follows. A recess having a large longest diameter of the opening (preferably a recess having a large shortest diameter of the opening) is sparsely arranged on the surface of the electrophotographic photosensitive member, and the area of the flat portion is particularly large among the portions other than the recess. Take. As a result, it has been found that the effect of suppressing image flow is dramatically improved. That is, a sufficient effect can be obtained for an image flow that occurs remarkably in the vicinity of the charging device, or an image flow immediately after startup that is likely to occur when the electrophotographic apparatus is left for several days in a high-temperature and high-humidity environment. all right.
By sparsely arranging the recesses with the longest diameter of the opening, chattering of the cleaning blade is moderately suppressed, and a stable rubbing state between the surface of the electrophotographic photosensitive member and the cleaning blade is created. At the same time, the pressure of the cleaning blade with respect to the recesses is relatively low, so that the pressure with respect to portions other than the recesses is relatively high. In addition to the concave portions where the pressure increases, the image flow causative substance adhering to the surface of the electrophotographic photosensitive member is increased by increasing the number of flat portions on which the surface of the electrophotographic photosensitive member can be efficiently refreshed. It becomes easy to be removed.
The present inventors believe that the image flow suppression effect is dramatically improved by such a mechanism.
Specifically, the surface of the electrophotographic photoreceptor is provided with a plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less. A plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less are also referred to as “specific recesses”.
The specific concave portion is a square region having a side of 500 μm (area is 250,000 μm) at an arbitrary position on the surface of the electrophotographic photosensitive member. ² ) Is provided (extracted) on the surface of the electrophotographic photosensitive member as follows. That is, the area of the specific recess in a square region having a side of 500 μm is 10000 μm. ² 90000μm or more ² It is provided to be as follows.
In addition, when the surface of the electrophotographic photosensitive member is a curved surface, it is as follows. For example, when the electrophotographic photosensitive member is cylindrical, the surface (circumferential surface) of the electrophotographic photosensitive member is a curved surface curved in the circumferential direction. In this case, “arranging a square region having a side of 500 μm at an arbitrary position on the surface of the electrophotographic photosensitive member” means that when the curved surface is corrected to a flat surface, the region that becomes a square in the flat surface is the electrophotographic photosensitive member. It means that it is arranged at an arbitrary position on the surface of.
In addition to the specific recess, a flat portion is provided on the surface of the electrophotographic photosensitive member. The flat portion is provided on the surface of the electrophotographic photosensitive member as follows. That is, when a square region having a side of 500 μm is arranged at an arbitrary position on the surface of the electrophotographic photosensitive member, the area of the flat portion in the square region having a side of 500 μm is 80000 μm. ² 240,000 μm ² It is provided to be as follows.
The specific concave portion or flat portion on the surface of the electrophotographic photosensitive member can be observed using a microscope such as a laser microscope, an optical microscope, an electron microscope, or an atomic force microscope.
As the laser microscope, for example, the following devices can be used. Keyence Corporation ultra-deep shape measurement microscope VK-8550, ultra-deep shape measurement microscope VK-9000, ultra-deep shape measurement microscope VK-9500, VK-X200. Surface shape measuring system Surface Explorer SX-520DR type machine manufactured by Ryoka System Co., Ltd. Scanning confocal laser microscope OLS3000 manufactured by Olympus Corporation. Real color confocal microscope Oplitex C130 manufactured by Lasertec Corporation.
As the optical microscope, for example, the following devices can be used. Keyence Corporation digital microscope VHX-500, digital microscope VHX-200. 3D digital microscope VC-7700 manufactured by OMRON Corporation.
As the electron microscope, for example, the following devices can be used. Keyence 3D Real Surface View Microscope VE-9800, 3D Real Surface View Microscope VE-8800. Scanning electron microscope conventional / variable pressure SEM manufactured by SII Nanotechnology. A scanning electron microscope SUPERSCAN SS-550 manufactured by Shimadzu Corporation.
As the atomic force microscope, for example, the following devices can be used. Nanoscale hybrid microscope VN-8000 manufactured by Keyence Corporation. Scanning probe microscope NanoNavi station manufactured by SII Nanotechnology. Scanning probe microscope SPM-9600 manufactured by Shimadzu Corporation.
The observation of the 500 μm square area and the observation for obtaining the image (C) described below may be performed at a low magnification or after a partial observation at a high magnification as long as the specific concave portion can be identified. A plurality of partial images may be connected using software or the like.
The determination (definition) of the specific recessed portion and the flat portion in a square region having a side of 500 μm will be described.
First, the surface of the electrophotographic photoreceptor is enlarged and observed with a microscope. For example, when the surface (circumferential surface) of the electrophotographic photosensitive member is a curved surface curved in the circumferential direction as in the case where the electrophotographic photosensitive member is cylindrical, a cross-sectional profile of the curved surface is extracted and a curved line ( If the electrophotographic photosensitive member is cylindrical, an arc) is fitted.
FIG. 7 shows an example of fitting. The example shown in FIG. 7 is an example when the electrophotographic photosensitive member is cylindrical. In FIG. 7, a solid line 701 is a cross-sectional profile of the surface (curved surface) of the electrophotographic photosensitive member, and a broken line 702 is a curve fitted to the cross-sectional profile 701. The cross-sectional profile 701 is corrected so that the curve 702 becomes a straight line, and a surface obtained by extending the obtained straight line in the longitudinal direction (direction perpendicular to the circumferential direction) of the electrophotographic photosensitive member is used as a reference surface. Even when the electrophotographic photosensitive member is not cylindrical, the reference surface is obtained in the same manner as when the electrophotographic photosensitive member is cylindrical.
The surface that is located 0.2 μm below the obtained reference surface and is parallel to the reference surface is the second reference surface, the surface that is 0.2 μm above the reference surface and is parallel to the reference surface is the third reference surface. To do. Of the square region having a side of 500 μm, a portion sandwiched between the second reference surface and the third reference surface is defined as a flat portion in the square region. A portion located above the third reference plane is defined as a convex portion in the square area. A portion located below the second reference plane is defined as a recess in the square area.
The distance from the second reference plane to the lowest point of the recess is defined as the depth of the recess. Let the cross section of the recessed part by a 2nd reference surface be an opening part of a recessed part, and let the length of the longest line segment be the longest diameter of the opening part of a recessed part among the line segments which cross an opening part.
The depth determined in this manner is in the range of 0.5 μm or more and 5 μm or less, and the longest diameter of the opening is in the range of 20 μm or more and 80 μm or less corresponds to the specific recess among the recesses. The depth of the specific recess in this example is preferably in the range of 1 μm to 5 μm. Further, the distance when the distance between the two parallel lines sandwiching the opening of the recess is the shortest is the shortest diameter of the opening of the recess. The shortest diameter of the opening of the specific recess in this example is preferably in the range of 20 μm to 80 μm.
1A and 1B, the relationship between the reference surface 101, the flat portion (the portion sandwiched between the second reference surface 102 and the third reference surface 103), the concave portion 104 (specific concave portion), the convex portion 105, and the like. This is shown schematically. 1A and 1B are cross-sectional profiles after the above correction.
2A to 2G show examples of the shape of the opening of the specific recess (the shape when the specific recess is viewed from above). Moreover, the example of the cross-sectional shape of a specific recessed part is shown to FIG. 3 (A)-(G).
Examples of the shape of the opening of the specific recess include a circle, an ellipse, a square, a rectangle, a triangle, a quadrangle, and a hexagon as shown in FIGS. Moreover, as a cross-sectional shape of a specific recessed part, as shown to FIG. 3 (A)-(G), what has edges, such as a triangle, a square, a polygon, the waveform which consists of a continuous curve, and a triangle , Quadrilaterals, polygonal edges partially or entirely deformed into curves, and the like.
The plurality of specific recesses provided on the surface of the electrophotographic photoreceptor may all have the same shape, the longest diameter and depth of the opening, or may have different shapes, the longest diameter and depth of the opening. It may be mixed.
The specific recess may be formed on the entire surface of the electrophotographic photosensitive member, or may be formed on a part of the surface of the electrophotographic photosensitive member. When the specific recess is formed on a part of the surface of the electrophotographic photosensitive member, it is preferable that the specific recess is formed at least in the entire contact area with the cleaning member.
In addition, the flat portion provided on the surface of the electrophotographic photosensitive member preferably has a certain size from the viewpoint of enhancing the removability of the substance causing the image flow, and there are few narrow flat portions (narrow portions). Is preferred. Specifically, the ratio of the area of the narrow portion where the 10 μm side square area cannot be arranged among the flat parts in the 500 μm side square area arranged at an arbitrary position on the surface of the electrophotographic photosensitive member is as follows. It is preferable that it seems. That is, it is preferably 30% or less with respect to the entire area of the flat portion in the square region having a side of 500 μm. However, even if the area of the narrow portion is 30% or more, the effect in this example can be obtained.
FIG. 10 is a diagram for explaining a narrow portion. FIG. 10 shows an example of a shape when a part of the surface of the electrophotographic photosensitive member is viewed from above. In FIG. 10, for ease of explanation, a case where all the portions that are not specific recesses are flat portions is taken as an example.
In FIG. 10, reference numeral 1001 denotes a specific concave portion on the surface of the electrophotographic photosensitive member, 1002 denotes a square region having a side of 10 μm arranged on the flat portion of the surface of the electrophotographic photosensitive member, and 1003 denotes a narrow portion (black in the drawing). The part that is filled). The square region 1002 may be arranged in any direction on the flat portion as indicated by a broken-line square in the drawing. A portion where the square region 1002 cannot be arranged in any direction in the flat portion becomes a narrow portion 1003 in the flat portion.
<Suppression of image quality degradation>
Next, feature 4 which is an item for suppressing image quality deterioration will be described. As a result of investigations by the present inventors, the image quality may be deteriorated by providing a plurality of recesses on the surface of the electrophotographic photosensitive member. The reason for this is that the concave portions tend to have inferior electrophotographic characteristics as compared with portions that are not concave portions. The electrophotographic characteristics are charging ability, latent image reproducibility, development efficiency or transfer efficiency. If the electrophotographic characteristics of the recess are inferior, the portion of the image data that is imaged in the recess of the electrophotographic photosensitive member cannot be faithfully reproduced. As a result, the output image is shaded according to the arrangement of the recesses, and the granularity (roughness) of the image is reduced.
Furthermore, when pseudo halftone processing formed with dots is used as a method of expressing gradations, moire is generated in addition to a decrease in graininess. The decrease in graininess (guzziness) and moire are caused by the following mechanism.
First, the halftone is converted into image data composed of a set of small dots called a screen by pseudo halftone processing. When the screen is imaged, the portion overlapping the concave portion is not faithfully reproduced, so that dots are lost. Since the degree of missing dots depends on the degree of overlap between the recesses and the dots, the missing dots are not uniform and vary. At this time, if the variation in dot missing is large, the graininess is lowered. Furthermore, depending on the relationship between the screen pattern and the arrangement of the recesses, the dot missing variation appears periodically. As a result, periodic shading, that is, moire occurs in the output image.
As a result of the study by the present inventors, when using pseudo halftone processing formed with dots as a method of expressing gradation, it is possible to suppress image quality degradation by arranging the concave portions so as to satisfy a specific standard. I understood. The deterioration in image quality is graininess (guzziness) and moire. An outline of these will be described.
First, a description will be given of a decrease in graininess (guzziness). Generally, an electrophotographic apparatus uses pseudo halftone processing as a technique for expressing gradation. The pseudo halftone processing is a method of expressing the gray scale by using only two colors of white and black to control the number of pixels and how the pixels are gathered. Of course, it can also be used for color.
There are various pseudo-halftone processing patterns (screens) such as parallel lines, wavy lines, and grain, but the method of representing them by a set of small dots is the mainstream. For pseudo halftone processing formed with dots, AM dot screening with regular dot placement and changing the dot size and density to express shading, irregular dot placement with fixed dot diameter, There is FM screening that expresses shading by changing the density. Although the following description will be given for AM screening, the pseudo halftone processing in this example may be either AM screening or FM screening.
FIG. 11A is an example of an enlarged screen by AM screening. On the other hand, the surface of the electrophotographic photoreceptor can be designed in various ways with respect to the size and arrangement of the recesses. FIGS. 11B and 11C show examples in which the opening of the recess is expressed in black and the portion other than the recess is expressed in white. (B) is an irregular arrangement of depressions with square openings and recess opening sizes close to the dot size. (C) is an irregular arrangement of depressions with square openings and small opening sizes with respect to the dot size. (B), (c) is an example for explanation, and is not limited to this.
The concave portion tends to deteriorate the electrophotographic characteristics, and in some cases, the concave portion is not image-formed. That is, when the above-described screen dots are formed on the recesses, the dots are missing. When the screen image of (a) is output using the electrophotographic photosensitive member in which the concave portions of (b) and (c) are arranged, the output images are assumed to be (d) and (e). Each dot is missing depending on the degree of overlap with the recess, and it can be seen that the variation in dot missing is larger in (d) than in (e).
Although the screen is enlarged here, the pseudo halftone process actually uses an optical illusion and is used with a dot size that cannot be recognized by the human eye. (F) and (g) show images obtained by reducing (d) and (e) to some extent. It can be seen that the variation in dot missing (f) is larger, the variation in shading is larger, and the graininess (grid) is reduced.
Next, moire will be described. In the example of the above-described decrease in graininess (gutteriness), the graininess (gutteriness) is reduced by a combination of a regular screen and an irregular recess arrangement. On the other hand, in the case of a combination of a regular screen and a regular recess arrangement, interference occurs between patterns, and dot missing variation (shading) appears periodically, so-called moire (interference fringes) occurs.
As an example of a regular screen, FIG. 12A shows a screen having a square arrangement and a square arrangement angle of 45 ° when the exposure light main scanning direction (horizontal direction in this figure) is 0 °. Show. As an example of the regular recess arrangement, (b) and (c) are shown in which the shape of the opening is circular and the arrangement is a square arrangement. (B) is a square arrangement angle of 41.2 °, and (c) is 26.6 °. When the screen image of (a) is output using the electrophotographic photosensitive member in which the concave portions of (b) and (c) are arranged, the output images are (d) and (e). When viewed microscopically, interference occurs in both (d) and (e), and the variation of dot missing appears periodically.
However, when (d) and (e) are viewed macroscopically, (d) is more prominent in periodic shading. This is because the longer the shade period, the higher the visual resolution. On the other hand, if the period of light and shade becomes very short as shown in (e), it will not be visually recognized as moiré by human eyes.
Further, the interference has a characteristic that the longer the period, that is, the lower the wave number, is when the concave portion is closer to the number of lines and the angle of the screen. In the recess arrangement of (b) and (c), the angle 41.2 ° of (b) is closer to the screen angle 45 ° of (a) than the angle 26.6 ° of (c).
As a result, the period of interference is longer in (d) than in (e), that is, it has a low wavenumber, and is therefore easily visible. Therefore, the problem of image quality is low wave number moire.
As described above, the technique of providing a plurality of concave portions on the surface of the electrophotographic photosensitive member has problems of image quality deterioration, that is, graininess reduction and moire.
<Image quality degradation index>
The calculation processes (1) to (3), which are methods for calculating the image quality degradation index (f), will be described in detail.
(1) From the screen pattern (B) generated by the pseudo halftone process formed with dots, the portion overlapping with the plurality of recesses is deleted to obtain an image (C).
This process is a process of creating a pseudo output image by image processing. The screen pattern (B) generated by the pseudo halftone process formed by dots is, for example, (a) in FIG. 11 and (a) in FIG. Images (C) obtained by deleting portions overlapping the plurality of recesses from the screen are, for example, (d) and (e) in FIG. 11 and (d) and (e) in FIG.
As described above, the concave portion tends to have inferior electrophotographic characteristics as compared with the non-concave portion, and the image is missing. The electrophotographic characteristics are charging ability, latent image reproducibility, development efficiency or transfer efficiency. Since the concave portion has a smaller thickness of the photosensitive layer than the non-recessed portion and has a large capacitance, or the contact with the charging member becomes insufficient, the charging ability may be lowered. In addition, the concave portion may have a lower photosensitive film thickness than the non-recessed portion, and the sensitivity may be reduced, or exposure light may be refracted due to the shape of the concave portion, thereby reducing the latent image reproducibility.
In addition, since the concave portion is insufficiently brought into contact with the transfer member and the toner carried on the developing member, the transfer efficiency and the developing efficiency may be lowered. The electrophotographic characteristics of the recesses do not necessarily deteriorate because they depend on the photosensitive layer, the size of the recesses, the toner, the electrophotographic process, or the surrounding environment.
However, an object in this example is to provide an electrophotographic apparatus in which image quality degradation due to the concave portion is suppressed under any conditions. Therefore, in calculating the image quality degradation index (f), image data Of these, the portion formed in the recess is treated as not printed.
The screen pattern (B) is generated by a pseudo halftone processing algorithm set in the electrophotographic apparatus when a gray scale is output by the electrophotographic apparatus. Therefore, the screen pattern (B) can be obtained from the gray scale density and the pseudo halftone processing algorithm. Alternatively, the screen pattern (B) can be obtained by setting the density, resolution, dot shape, and number of lines using Adobe Photoshop (registered trademark) or the like.
Note that in the case of an electrophotographic apparatus using multi-value pseudo halftone processing using PWM (pulse width modulation) or the like, binarization is performed with a half-value (50%) threshold value of multi-value information, and a screen pattern ( B).
The screen pattern (B) can also be obtained by observing a toner image formed on the photoreceptor. Specifically, image output is performed using a photoconductor that does not have a concave shape on the surface, and the electrophotographic apparatus is turned off during output to stop the image with a toner image on the photoconductor. As a result, a toner image without image quality deterioration is obtained on the photoreceptor. A micrograph of the screen pattern (B) can be obtained by observing the toner image on the photoreceptor with a microscope such as the above-mentioned laser microscope or optical microscope.
Subsequently, image processing is performed on the obtained micrograph to generate binarized image data. Any method may be used for generating the binarized image data. For example, the obtained micrograph is obtained by performing the following binarization process.
If the photoconductor is a cylindrical body, the curvature component is corrected (similar to the fitting shown in FIG. 7 above).
-Remove noise components while leaving edges with median filter
-Binarization with 50% threshold of difference between minimum luminance (toner image) and maximum luminance (photoconductor)
・ Removing minute area (removing fine particles such as minute toner)
・ Fill the area surrounded by the toner image (fill hole)
Such an image processing calculation can be performed using particle analysis software (GRADING ANALYSIS) manufactured by Keyence Corporation.
The arrangement (A) of the plurality of recesses on the photoreceptor is also obtained by observation and binarization processing using a microscope such as the above-mentioned laser microscope, optical microscope, electron microscope, and atomic force microscope. The binarization process can be performed by the same method as the image process used in the screen pattern (B). However, since the specific recess is a portion below the second reference plane, it is necessary to reflect the opening shape of the specific recess determined by a microscope capable of obtaining three-dimensional information. Alternatively, by using analysis software attached to a microscope capable of obtaining three-dimensional information, the obtained micrograph can be binarized directly above and below the second reference plane.
In addition, when the method of forming the recesses on the surface of the photoreceptor is a method of pressing a mold having projections, which will be described later, to the surface of the electrophotographic photoreceptor, the outer peripheral shape of the mold protrusions and the recesses on the surface of the photoreceptor The recesses can be formed so that the opening shapes are the same. Therefore, it is good also as arrangement | positioning of a recessed part with the electronic data at the time of mold observation or a mold design.
Also, when the method of forming the recess is laser light irradiation described later, the recess can be formed so that the opening shape of the recess is the same as the opening shape of the mask. Therefore, it is good also as arrangement | positioning of a recessed part with the electronic data at the time of observation of a laser mask, or designing a mask.
The shape of the image (C), that is, the arrangement of the plurality of recesses on the photoconductor (A) and the acquired shape of the screen pattern (B) contribute as much as possible in order to correctly evaluate the moire generated in a specific direction. Are equally preferred, and squares and circles are preferred.
The area of the image (C), that is, the acquired areas of (A) and (B) is 400 dots or more of the screen pattern (B) from the viewpoint of the reliability of the standard deviation (σ) of the dot area described later. Area is preferred. In order to correctly evaluate the image quality, an appropriate area is selected from human visual characteristics. For example, it can be determined from a VTF function (visual spatial frequency characteristic) representing visual resolving power with respect to wave number (line number) shown in FIG. FIG. 13 is a VTF function with an observation distance of 300 mm, in which the vertical axis represents visual sensitivity and the horizontal axis represents wave number (number of lines).
In FIG. 13, the visual sensitivity (vertical axis) when the wave number (horizontal axis) is about 1 (lpi) is sufficiently low, that is, even if the density change occurs at a cycle longer than 1 (lpi), It is invisible to the eyes. Therefore, the acquisition area can be a square region having one side of 25.4 mm.
Alternatively, a square region having a side of 21.2 mm can be formed in accordance with the image quality attribute and the measurement method shown in ISO 13660. Alternatively, the standard deviation (σ) of the dot area, which will be described later, can be greater than or equal to the area that does not depend on the acquisition area. For example, if the patterns (A) and (B) are homogeneous, the standard deviation (σ) of the dot area does not depend on the acquired area even if the acquired area is small. Therefore, the acquisition area can be appropriately set according to the patterns (A) and (B).
In the embodiment, the area where (σ) does not depend on the acquired area is verified. The acquisition range of the plurality of recesses (A) and the screen pattern (B) on the photoconductor was a 10.84 mm square area (corresponding to 1024 dots at 10.84 mm = 2400 dpi). However, it goes without saying that the ranges of (A) and (B) in this example may be set appropriately from the above viewpoint, and may not be a square region of 10.84 mm.
When the arrangement range (A) of the plurality of recesses on the photoconductor and the acquisition range of the screen pattern (B) are wide, the image connection function of the above-described microscope group is effective. Or you may acquire using the GX-700 by Rebox Co., Ltd. which can image | photograph a wide area with a CCD camera. FIG. 17 shows a photograph of the surface of the electrophotographic photosensitive member having recesses, acquired by GX-700. This CCD photograph can be binarized to form a plurality of concave portions (A) and a screen pattern (B). In the case of the arrangement (A) of a plurality of recesses, it is preferable that the shape of the specific recess is grasped by the above-described microscope group and reflected in the binarized image.
Further, when the screen pattern (B) generated by the pseudo halftone process formed by dots is acquired by microscopic observation, the following can be performed if AM screening is performed. That is, based on the result of partial microscopic observation, commercially available software can be used to generate binarized image data having a large area. After obtaining a micrograph of a part and binarization processing, the resolution can be determined from the dot diameter. Furthermore, in the main scanning direction and the sub-scanning direction of image exposure, the distance between the adjacent shortest dots can be measured and the angle and the number of lines can be determined by calculation. As an example, Table 1 shows a case of a square arrangement with a resolution of 2400 dpi.
For example, when the adjacent shortest dot interval measured from the binarized image is 2 dots for main scanning and 9 dots for sub scanning, it can be said that the dot period is 3 periods for main scanning and 10 periods for sub scanning. When the intersection of 3 main scanning cycles and 10 sub-scanning cycles is seen in Table 1, it can be seen that the screen angle is 73.3 ° and the number of lines is 230 (lpi). If the resolution, angle, and number of lines can be grasped in this way, a large-area binarized image data is generated using the conversion method from Adobe Photoshop's gray scale to monochrome two-tone (halftone screen). can do.
The same method can be used for the arrangement (A) of the plurality of recesses on the photoreceptor when they are arranged as in the AM screening. The image quality degradation index (f) may be calculated using the binarized image data generated as described above.
In any of the above-described means, when grasping the arrangement (A) of the plurality of concave portions of the photosensitive member, the opening shape of the specific concave portion is determined according to the criteria described in FIG.
(2) Particle analysis is performed on the image (C), and an average value SM of dot areas and a standard deviation (σ) of dot areas are calculated.
Particle analysis is performed on the image (C) that is a binary image, and the individual areas of all the dots in the image (C) are grasped. The particle analysis can be performed using commercially available software such as Keyence Corporation particle analysis software (GRADING ANALYSIS). Based on this data, an average value SM of dot areas and a standard deviation (σ) of dot areas are calculated.
The average value SM of the dot areas is the dot area S _i Is the arithmetic average (value) obtained by dividing the total sum by the number n of all dots, and is obtained by the equation (2).
The standard deviation (σ) of the dot area indicates the area of a dot as S _i When the number of all dots is n, the dispersion (σ ² ) And is a value representing the degree of variation in dot area. The standard deviation (σ) of the dot area means that the smaller the value, the smaller the dot area variation, and the lower the image quality, that is, the graininess (cracking) and the moire are suppressed.
(3) Obtain the image quality degradation index (f) by the following formula (1).
Since the standard deviation (σ) of the dot area depends on the average value SM of the dot areas, the image quality degradation of the screen pattern (B) having a large dot diameter and the screen pattern (B) having a small dot diameter are simply compared. I can't. Therefore, for standardization, the standard deviation (σ) of the dot area is divided by the average value SM of the dot areas.
As a result of investigations by the present inventors, it is possible to suppress the deterioration of the image quality by arranging the recesses so that the image quality degradation index (f) obtained by quantifying the degree of decrease in the variation of the dot defect described above becomes 14% or less. I understood. When the image quality degradation index (f) is 14% or less, it means that variation in dot missing is small, and graininess degradation and moire are suppressed.
<Arrangement of recesses on the surface of the electrophotographic photoreceptor>
The recess arrangement in which the image quality degradation index (f) is 14% or less is not limited as long as the features 1 to 3 that are items for suppressing image flow are satisfied. Separately, there is a method of suppressing image quality deterioration by using FM halftone processing instead of the concave portion arrangement, but FM screening itself tends to reduce the roughness. Therefore, in electrophotographic apparatuses, AM screening and FM screening are generally used according to the required image quality.
In order to perform the concave arrangement for reducing the image quality degradation index for AM screening, for example, a method of mixing a plurality of types of opening diameters of the concave parts can be mentioned. Further, there is a method in which the opening diameter of the recesses or the density of the recesses is much larger or smaller than the dot diameter of the screen pattern (B). However, the opening diameter of the recesses and the density of the recesses have an appropriate range for image flow suppression, which is another effect, and the AM screening pattern is designed because the dot diameter and density change depending on the density and resolution. Tend to be narrower. The following two methods are effective for designing the recess arrangement.
One is a method of optimizing the direction of the arrangement of the concave portions with respect to the AM screening pattern by the pseudo halftone process formed by regularly arranging the concave portions and the dots to be output. In the case where the concave portions are regularly arranged, the granularity (roughness) is not easily lowered, but low wave number moire is likely to occur. Low wave number moire is likely to occur when the concave portion arrangement is close to the number of lines and angle of the pattern of the pseudo halftone processing, so the arrangement angle of the concave portion arrangement and the screen pattern angle should be arranged as close to orthogonal as possible. Thus, the image quality degradation index (f) can be lowered.
The other is a method of irregularly arranging the recesses. When the concave portions are regularly arranged, for example, in a tandem machine, the angle of the AM screening pattern is different for each color. Therefore, it is necessary to design the concave portion according to each color, and the design freedom is narrowed. On the other hand, if the concave portions are irregularly arranged, the image quality degradation index (f) can be lowered at any AM screening pattern angle. However, since the granularity (roughness) tends to be lower than when the recesses are regularly arranged, it is preferable to design the recesses together with the opening diameter and density.
As a means for irregularly arranging the concave portions on the surface of the photoreceptor, any method may be used as long as the image quality degradation index (f) can be lowered. In particular, when the method of forming the recesses on the surface of the photoconductor is a method that can intentionally control the arrangement of the recesses, an FM screening technique, which is one of pseudo halftone processing, can be applied to the design. it can. The method of intentionally controlling the arrangement of the concave portions includes a method of pressing a mold having a convex portion, which will be described later, against the surface of the electrophotographic photosensitive member, and a method of forming the concave portions by laser light irradiation.
FM screening is a pseudo halftone process in which the dot diameter is fixed, irregular dot arrangement is performed, and gradation is expressed by changing the dot density. The offset printing machine, the electrophotographic printer, and the inkjet method are used. It is used in many image forming apparatuses. An irregular recess arrangement can be designed using a randomizing algorithm that generates an irregular dot arrangement for FM screening. Various randomization algorithms have been developed, and any method may be used as long as the image quality degradation index (f) becomes low.
In the embodiment, the Floyd-Steinberg method is used among error diffusion which is the most general FM screening. The Floyd-Steinberg method distributes a difference (error) between a signal value of a target pixel of image data and a signal value when the target pixel is binarized to neighboring pixels.
An example is shown in FIG. In this figure, 7/16 of the error of the pixel of interest is added to the signal value of the pixel right next to the pixel of interest. The error of the pixel of interest is distributed to the lower right, lower, and lower left pixels at the rate shown in the figure. The other pixels reflect this distribution result and binarize sequentially. As a result, a pattern having a non-periodic characteristic as shown in (b) can be generated. At this time, it is possible to design an arbitrary recess opening size, recess density, and recess arrangement by changing the pixel size, the distribution ratio, and the number of pixels to be distributed.
<Method for forming recesses on the surface of an electrophotographic photoreceptor>
The method for forming the recess is not particularly limited as long as the method can satisfy the requirements for the recess. For example, a method for forming the surface of an electrophotographic photosensitive member by irradiation with laser light having an output characteristic with a pulse width of 100 ns (nanoseconds) or less, and a shape transfer by pressing a mold having a predetermined shape against the surface of the electrophotographic photosensitive member The method of performing is mentioned.
A method of forming a recess by laser light irradiation having an output characteristic with a pulse width of 100 ns (nanoseconds) or less will be described.
Specific examples of the laser used in this method include an excimer laser using a gas such as ArF, KrF, XeF or XeCl as a laser medium or a femtosecond laser using titanium sapphire as a medium. Furthermore, the wavelength of the laser beam in the laser irradiation is preferably 1,000 nm or less.
The excimer laser is laser light emitted in the following steps. First, high energy such as discharge, electron beam or X-ray is applied to a mixed gas of a rare gas such as Ar, Kr or Xe and a halogen gas such as F or Cl to excite the above elements. And combine them. Thereafter, excimer laser light is emitted when dissociating by falling to the ground state. Examples of the gas used in the excimer laser include ArF, KrF, XeCl, and XeF, and any of them may be used. In particular, KrF or ArF is preferable.
As a method for forming the concave portion, a mask in which a laser light blocking portion 2601 and a laser light transmitting portion 2602 are appropriately arranged as shown in FIG. Only laser light that has passed through the mask is condensed by the lens and irradiated onto the workpiece, so that a recess having a desired shape and arrangement can be formed. Since a large number of recesses within a certain area can be processed simultaneously instantly regardless of their shape and area, the process can be performed in a short time. Several mm per irradiation by laser irradiation using a mask ² To several centimeters ² Is processed.
In laser processing, as shown in FIG. 15B, first, the electrophotographic photosensitive member 2704 as a work is rotated by a work rotating motor 2702. While rotating, the workpiece moving device 2703 shifts the laser irradiation position of the laser oscillation unit 2701 in the axial direction of the electrophotographic photosensitive member 2704, thereby efficiently forming concave portions over the entire surface of the electrophotographic photosensitive member 2704. Can do. The depth of the concave portion can be adjusted within a desired range depending on the irradiation time and the number of irradiation times of the laser beam. According to such a configuration, it is possible to realize rough surface machining with high controllability of the size, shape, and arrangement of the recesses, and with high accuracy and high flexibility.
Next, a method for forming a recess for transferring a shape by pressing a mold having a protrusion corresponding to the recess to be formed to the surface of the electrophotographic photosensitive member will be described. FIG. 4 shows an example of a press-contact shape transfer processing apparatus for forming concave portions on the surface of the electrophotographic photosensitive member.
According to the press-fitting shape transfer processing apparatus shown in FIG. 4, while rotating the electrophotographic photosensitive member 401 as a workpiece, the mold 402 is continuously brought into contact with the surface (circumferential surface) and pressurized, thereby allowing the electron to move. A concave portion or a flat portion can be formed on the surface of the photoconductor 401.
Examples of the material of the pressure member 403 include metal, metal oxide, plastic, and glass. Among these, stainless steel (SUS) is preferable from the viewpoint of mechanical strength, dimensional accuracy, and durability. The pressure member 403 is provided with a mold on the upper surface thereof. Further, the mold 402 can be brought into contact with the surface of the electrophotographic photosensitive member 401 supported by the support member 404 with a predetermined pressure by a support member (not shown) on the lower surface side and a pressure system (not shown). Further, the support member 404 may be pressed against the pressure member 403 with a predetermined pressure, or the support member 404 and the pressure member 403 may be pressed against each other.
The example shown in FIG. 4 is an example in which the surface of the electrophotographic photosensitive member 401 is continuously processed while being driven or driven and rotated by moving the pressing member 403. Further, the surface of the electrophotographic photosensitive member 401 is continuously processed by fixing the pressure member 403 and moving the support member 404 or by moving both the support member 404 and the pressure member 403. You can also. Note that it is preferable to heat the mold 402 and the electrophotographic photosensitive member 401 from the viewpoint of efficiently performing shape transfer.
Examples of the mold include a fine surface-treated metal and resin film, and a silicon wafer surface patterned with a resist. Moreover, what gave the metal coating to the resin film in which microparticles | fine-particles were disperse | distributed and the resin film which has a fine surface shape is mentioned. Moreover, it is preferable to install an elastic body between the mold and the pressure member from the viewpoint of making the pressure pressed against the electrophotographic photosensitive member uniform.
<Configuration of electrophotographic photoreceptor>
The electrophotographic photoreceptor of this example has a support and a photosensitive layer formed on the support. Examples of the shape of the electrophotographic photosensitive member include a cylindrical shape, a belt (endless belt) shape, and a sheet shape.
The photosensitive layer may be a single-layer type photosensitive layer containing a charge transport material and a charge generation material in the same layer, or a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. It may be a laminated type (functionally separated type) photosensitive layer separated. From the viewpoint of electrophotographic characteristics, a laminated photosensitive layer is preferred. Further, the laminated photosensitive layer may be a normal photosensitive layer in which the charge generation layer and the charge transport layer are laminated in this order from the support side, or a reverse layer in which the charge transport layer and the charge generation layer are laminated in this order from the support side. Type photosensitive layer. From the viewpoint of electrophotographic characteristics, a normal layer type photosensitive layer is preferred. In addition, the charge generation layer may have a stacked structure, and the charge transport layer may have a stacked structure.
The support is preferably one that exhibits conductivity (conductive support). Examples of the material of the support include metals (alloys) such as iron, copper, gold, silver, aluminum, zinc, titanium, lead, nickel, tin, antimony, indium, chromium, aluminum alloy, and stainless steel. In addition, for example, a metal support or a plastic support having a film formed by vacuum deposition using aluminum, an aluminum alloy, or an indium oxide-tin oxide alloy can be used.
In addition, a support obtained by impregnating plastic or paper with conductive particles such as carbon black, tin oxide particles, titanium oxide particles, and silver particles, or a support made of conductive binder resin can also be used.
The surface of the support may be subjected to, for example, a cutting process, a roughening process, or an alumite process for the purpose of suppressing interference fringes due to scattering of laser light.
Between the support and the undercoat layer or photosensitive layer (charge generation layer, charge transport layer) described later, for example, for the purpose of suppressing interference fringes due to scattering of laser light, and covering scratches on the support, A conductive layer may be provided. The conductive layer is formed, for example, by applying a coating solution for a conductive layer obtained by dispersing carbon black, a conductive pigment, a resistance adjusting pigment in a solvent together with a binder resin, and drying the obtained coating film. can do. Moreover, you may add to the coating liquid for conductive layers the compound which hardens and polymerizes by heating, ultraviolet irradiation, and radiation irradiation, for example. For example, the surface of a conductive layer in which a conductive pigment or a resistance adjusting pigment is dispersed tends to be roughened.
Examples of the binder resin used for the conductive layer include acrylic resin, allyl resin, alkyd resin, ethyl cellulose resin, ethylene-acrylic acid copolymer, epoxy resin, casein resin, silicone resin, gelatin resin, and phenol resin. In addition, a butyral resin, a polyacrylate resin, a polyacetal resin, a polyamideimide resin, a polyamide resin, a polyallyl ether resin, a polyimide resin, a polyurethane resin, a polyester resin, a polycarbonate resin, and a polyethylene resin can be given.
In addition, polyvinyl chloride, polyvinyl acetate, polyvinyl acetal, polystyrene resin, polysulfone resin, polyvinyl alcohol resin, and polyphenylene oxide are exemplified. Examples thereof include polyvinyl fluoride, polybutadiene resin, polypropylene resin, melamine resin, urea resin, agarose resin, and cellulose resin.
Examples of the conductive pigment and the resistance adjusting pigment include particles of metal (alloy) such as aluminum, zinc, copper, chromium, nickel, silver, and stainless steel, and those obtained by vapor deposition on the surface of plastic particles. It is also possible to use metal oxide particles such as zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin-doped indium oxide, antimony or tantalum-doped tin oxide. it can.
These may be used alone or in combination of two or more. When two or more types are used in combination, they may be mixed, or may be in the form of a solid solution or fusion. Further, the conductive pigment and the resistance adjusting pigment can be subjected to a surface treatment. As the surface treatment agent, for example, a surfactant, a silane coupling agent, or a titanium coupling agent is used.
Furthermore, for the purpose of light scattering, particles such as silicone resin fine particles and acrylic resin fine particles may be added. Moreover, you may contain additives, such as a leveling agent, a dispersing agent, antioxidant, a ultraviolet absorber, a plasticizer, a rectifying material.
The thickness of the conductive layer is preferably 0.2 μm or more and 40 μm or less, more preferably 1 μm or more and 35 μm or less, and more preferably 5 μm or more and 30 μm or less.
Between the support or conductive layer and the photosensitive layer (charge generation layer, charge transport layer), improvement of adhesion of the photosensitive layer, improvement of coating property, improvement of charge injection from the support, electrical breakdown of the photosensitive layer For the purpose of protecting the surface, an undercoat layer (intermediate layer) may be provided. The constituent material of the undercoat layer is not particularly limited as long as it satisfies the function. For example, it may be composed of a single resin or a mixture of a resin and a metal oxide.
The undercoat layer composed of a single resin can be formed by applying an undercoat layer coating solution obtained by dissolving a resin (binder resin) in a solvent, and drying the resulting coating film. it can.
Examples of the resin used for the undercoat layer composed of a single resin include polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, and an ethylene-acrylic acid copolymer. Further, casein, polyamide, N-methoxymethylated 6 nylon, copolymer nylon, glue and gelatin can be mentioned.
The thickness of the undercoat layer formed of a single resin is preferably 0.05 μm or more and 7 μm or less, and more preferably 0.1 μm or more and 2 μm or less.
The undercoat layer composed of a mixture of a resin and a metal oxide is obtained by applying a coating solution for an undercoat layer obtained by dispersing metal oxide particles in a solvent together with a binder resin. It can be formed by drying.
The metal oxide particles contained in the undercoat layer composed of a mixture of resin and metal oxide contain at least one selected from the group consisting of titanium oxide, zinc oxide, tin oxide, zirconium oxide, and aluminum oxide. It is preferable that the particles are. Among the particles containing the above metal oxide, particles containing zinc oxide are more preferable.
The metal oxide particles are particles in which the surface of the metal oxide particles is treated with a surface treatment agent such as a silane coupling agent in order to suppress black spot-like image defects due to charge injection from the support to the photosensitive layer side. There may be.
Examples of the silane coupling agent include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, and (phenylaminomethyl) methyldimethoxysilane. Examples thereof include N-2- (aminoethyl) -3-aminoisobutylmethyldimethoxysilane, N-ethylaminoisobutylmethyldiethoxysilane, and N-methylaminopropylmethyldimethoxysilane.
Moreover, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, methyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane are mentioned. Examples include 3-methacryloxypropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane.
Examples of the resin contained in the undercoat layer composed of a mixture of resin and metal oxide include acrylic resin, allyl resin, alkyd resin, ethyl cellulose resin, ethylene-acrylic acid copolymer, epoxy resin, casein resin, and silicone resin. Is mentioned. Examples include gelatin resin, phenol resin, urethane resin, butyral resin, polyacrylate resin, polyacetal resin, polyamideimide resin, polyamide resin, polyallyl ether, polyimide resin, polyester resin, and polyethylene resin.
In addition, polycarbonate resin, polystyrene resin, polysulfone resin, polyvinyl alcohol resin, polybutadiene resin, and polypropylene resin can be used.
Among these, it is preferable to use a urethane resin having low hygroscopicity from the viewpoint of suppressing potential fluctuation under a high temperature and high humidity environment.
The urethane resin suitably used for the undercoat layer composed of a mixture of a resin and a metal oxide is composed of a polymer of a composition of an isocyanate compound or a blocked isocyanate compound and a polyol resin.
Examples of the blocked isocyanate compound include those obtained by blocking 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and diphenylmethane-4,4′-diisocyanate with a blocking agent. Examples include 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI) blocked with a blocking agent. Examples include hexamethylene diisocyanate (HDI), HDI-trimethylolpropane adduct, HDI-isocyanurate, and HDI-biuret blocked with a blocking agent.
Examples of the blocking agent for the blocked isocyanate compound include oxime compounds such as formaldehyde oxime, acetoald oxime, methyl ethyl ketoxime, cyclohexanone oxime, acetone oxime, and methyl isobutyl ketoxime. Examples include active methylene compounds such as Meldrum's acid, dimethyl malonate, diethyl malonate, di-n-butyl malonate, ethyl acetate, and acetylacetone.
Further, amine compounds such as diisopropylamine, diphenylaniline, aniline and carbazole, and imine compounds such as ethyleneimine and polyethyleneimine can be mentioned. Examples include acid imide compounds such as succinimide and maleic imide, and imidazole compounds such as malonate, imidazole, benzimidazole and 2-methylimidazole. Examples include triazole compounds such as 1,2,3-triazole, 1,2,4-triazole, 4-amino-1,2,4-triazole, and benzotriazole.
Also, acid amide compounds such as acetanilide, N-methylacetamide, acetic acid amide, lactam compounds such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and urea compounds such as urea, thiourea, ethyleneurea, etc. It is done. Examples thereof include sulfites such as sodium bisulfite, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, and phenol compounds such as phenol and cresol.
Further, pyrazole compounds such as pyrazole, 3,5-dimethylpyrazole, and 3-methylpyrazole, and alcohol compounds such as methanol, ethanol, 2-propanol, and n-butanol can be used.
Moreover, the blocked isocyanate compound which combined 1 type (s) or 2 or more types of these blocking agents may be sufficient. Examples of the polyol resin include a polyvinyl acetal resin and a polyphenol resin.
The content ratio between the metal oxide particles and the resin is preferably 2: 1 to 4: 1 (mass ratio) of metal oxide particles: resin from the viewpoint of electrophotographic characteristics and crack suppression.
Examples of the dispersion method include a method using a homogenizer, an ultrasonic disperser, a ball mill, a sand mill, a roll mill, a vibration mill, an attritor, and a liquid collision type high-speed disperser.
The undercoat layer composed of a resin and metal oxide mixture further contains organic resin particles and a leveling agent, for example, for the purpose of adjusting the surface roughness of the undercoat layer or reducing cracks in the undercoat layer. You may let them. As the organic resin particles, hydrophobic organic resin particles such as silicone particles and hydrophilic organic resin particles such as cross-linked polymethacrylate resin (PMMA) particles can be used.
Various additives can be contained in the undercoat layer composed of a mixture of a resin and a metal oxide. Examples of the additive include metals such as aluminum powder and copper powder, and conductive substances such as carbon black. Examples thereof include electron transporting substances such as quinone compounds, fluorenone compounds, oxadiazole compounds, diphenoquinone compounds, alizarin compounds, and benzophenone compounds. Examples thereof include electron transport materials such as polycyclic condensed compounds and azo compounds. Organic metal compounds such as metal chelate compounds and silane coupling agents can be mentioned.
When the conductive layer is provided, the thickness of the undercoat layer composed of a resin and metal oxide mixture is preferably 0.5 μm or more and 10 μm or less, and more preferably 2 μm or more and 8 μm or less. . When the conductive layer is not provided, the thickness is preferably 10 μm or more and 40 μm or less, and more preferably 15 μm or more and 25 μm or less.
When the photosensitive layer is a laminated photosensitive layer, the charge generation layer is formed by applying a charge generation layer coating solution obtained by dispersing a charge generation material together with a binder resin and a solvent, and drying it. Can do. The coating solution for the charge generation layer may be prepared by adding only the charge generation material to the solvent and then dispersing the resin, and then adding the resin, or by adding both the charge generation material and the resin to the solvent and dispersing the preparation. Also good. The charge generation layer may be a vapor generation film of a charge generation material.
Examples of the charge generating material used in the photosensitive layer include azo pigments, phthalocyanine pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, squarylium dyes, thiapyrylium salts, triphenylmethane dyes, and quinacridone pigments. Examples include azulenium salt pigments, cyanine dyes, anthanthrone pigments, pyranthrone pigments, xanthene dyes, quinoneimine dyes, and styryl dyes.
These charge generation materials may be used alone or in combination of two or more. Among these, oxytitanium phthalocyanine, chlorogallium phthalocyanine, and hydroxygallium phthalocyanine are preferable from the viewpoint of sensitivity. Furthermore, among the hydroxygallium phthalocyanines, there are hydroxygallium phthalocyanine crystals having crystal forms having strong peaks at Bragg angles 2θ of 7.4 ° ± 0.3 ° and 28.2 ° ± 0.3 ° in CuKα characteristic X-ray diffraction. preferable.
Examples of the binder resin used for the charge generation layer include polycarbonate resin, polyester resin, butyral resin, polyvinyl acetal resin, acrylic resin, vinyl acetate resin, and urea resin. Among these, a butyral resin is preferable. These may be used alone or in combination as a mixture or copolymer.
Examples of the dispersion method include a method using a homogenizer, an ultrasonic disperser, a ball mill, a sand mill, a roll mill, and an attritor.
The ratio of the charge generation material and the binder resin in the charge generation layer is preferably 0.3 parts by mass or more and 10 parts by mass or less of the charge generation material with respect to 1 part by mass of the binder resin. If necessary, for example, a sensitizer, a leveling agent, a dispersant, an antioxidant, an ultraviolet absorber, a plasticizer, and a rectifying material can be added to the charge generation layer. The thickness of the charge generation layer is preferably from 0.01 μm to 5 μm, and more preferably from 0.1 μm to 2 μm.
When the photosensitive layer is a laminated photosensitive layer, a charge transport layer is formed on the charge generation layer. The charge transport layer can be formed by applying a charge transport layer coating solution obtained by dissolving a charge transport material and a binder resin in a solvent and drying it.
Examples of the charge transport material used in the photosensitive layer include pyrene compounds, N-alkylcarbazole compounds, hydrazone compounds, N, N-dialkylaniline compounds, diphenylamine compounds, and triphenylamine compounds. Examples include triphenylmethane compounds, pyrazoline compounds, styryl compounds, stilbene compounds, and butadiene compounds. These charge transport materials may be used alone or in combination of two or more. Among these charge transport materials, a triphenylamine compound is preferable from the viewpoint of charge mobility.
Examples of the binder resin used for the charge transport layer include acrylic resin, acrylonitrile resin, allyl resin, alkyd resin, epoxy resin, silicone resin, phenol resin, phenoxy resin, polyacrylamide resin, and polyamideimide resin. Examples include polyamide resins, polyallyl ether resins, polyarylate resins, polyimide resins, polyurethane resins, polyester resins, and polyethylene resins. Examples include polycarbonate resin, polysulfone resin, polyphenylene oxide resin, polybutadiene resin, polypropylene resin, and methacrylic resin.
Among these, insulating resins such as polyarylate resin, polycarbonate, polyvinyl butyral, polyvinyl acetate, polyvinyl pyridine resin, polyvinyl alcohol, polyvinyl pyrrolidone, agarose resin, cellulose resin, and casein are exemplified.
These may be used alone or in combination as a mixture or copolymer. Moreover, organic photoconductive polymers, such as poly-N-vinyl carbazole, polyvinyl anthracene, polyvinyl porene, can also be used. Further, a compound having a charge transport function introduced into the main chain or side chain of these resins to form a polymer charge transport material can also be used.
If necessary, for example, an antioxidant, an ultraviolet absorber, a plasticizer, and a leveling agent can be added to the charge transport layer.
The ratio of the charge transport material and the binder resin in the charge transport layer is preferably 0.3 parts by mass or more and 10 parts by mass or less of the charge transport material with respect to 1 part by mass of the binder resin.
When the charge transport layer is a single layer, the thickness of the charge transport layer is preferably 5 μm or more and 40 μm or less, and more preferably 8 μm or more and 30 μm or less. When the charge transport layer has a laminated structure, the thickness of the charge transport layer on the support side is preferably 5 μm to 30 μm, and the thickness of the charge transport layer on the surface side is preferably 1 μm to 10 μm. preferable.
In this example, when the charge transport layer is the surface layer of the electrophotographic photosensitive member, the charge transport layer is preferably composed of a resin having excellent wear resistance from the viewpoint of improving the durability of the electrophotographic photosensitive member. .
For the purpose of improving the abrasion resistance and cleaning properties of the electrophotographic photoreceptor, a protective layer may be formed on the photosensitive layer or the charge transport layer to form a surface layer. The protective layer can be formed by forming a coating film of a coating liquid for protective layer obtained by dissolving a resin (binder resin) excellent in abrasion resistance in a solvent, and drying the coating film.
Examples of the resin used for the protective layer include polyvinyl butyral resin, polyester resin, polycarbonate resin, polyamide resin, polyimide resin, and polyarylate resin. Examples include polyurethane resins, phenol resins, styrene-butadiene copolymers, styrene-acrylic acid copolymers, and styrene-acrylonitrile copolymers.
The protective layer is formed by forming a coating film of a coating solution for the protective layer obtained by dissolving a polymerizable monomer or oligomer in a solvent, and curing (polymerizing) the coating film using a crosslinking or polymerization reaction to protect it. A layer may be formed. Examples of the polymerizable monomer or oligomer include a compound having a chain polymerizable functional group such as an acryloyloxy group and a styryl group, and a compound having a sequentially polymerizable functional group such as a hydroxyl group, an alkoxysilyl group, an isocyanate group, and an epoxy group. Is mentioned.
Examples of the curing reaction include radical polymerization, ionic polymerization, thermal polymerization, photopolymerization, radiation polymerization (electron beam polymerization), plasma CVD method, and photo CVD method.
Moreover, since the characteristics required for the protective layer are both the strength of the film and the charge transport capability, conductive particles and a charge transport material may be added to the protective layer coating solution. As the conductive particles, a conductive pigment used in the conductive layer can be used. As the charge transport material, the above-described charge transport materials can be used.
Furthermore, it is more preferable to use a compound having both a charge transporting structure (preferably a hole transporting structure) and a polymerizable functional group in the same molecule from the viewpoint of achieving both the strength of the film and the charge transporting capability. From the viewpoint of maintaining electrophotographic characteristics, the polymerizable functional group is preferably an acryloyloxy group. Further, from the viewpoint of improving wear resistance, a compound having two or more polymerizable functional groups in the same molecule is preferable. In addition, a compound having both a charge transporting structure and a polymerizable functional group in the same molecule and the above-described charge transporting material, binder resin, polymerizable monomer or oligomer may be mixed and used.
In addition, a filler can be added to the surface layer (charge transport layer or protective layer) of the electrophotographic photoreceptor to improve durability. Examples of the filler include organic resin particles such as fluorine atom-containing resin particles and acrylic resin particles, and inorganic particles such as alumina, silica, and titania.
Additives can also be added for the purpose of improving various functions. Examples of the additive include conductive particles, an antioxidant, an ultraviolet absorber, a plasticizer, and a leveling agent.
When the protective layer has a charge transporting capability, a protective layer that also serves as one charge transporting layer may be provided on the charge generation layer to form a surface layer.
The thickness of the protective layer is preferably from 0.1 to 30 μm, and more preferably from 1 to 10 μm.
When the photosensitive layer is a single-layer type photosensitive layer, the photosensitive layer is one or two of the group of the charge generation material, the charge transport material, and the binder resin used for the charge generation layer, the charge transport layer, and the protective layer. A coating solution for a single-layer type photosensitive layer obtained by dissolving at least a binder resin in a solvent is applied. And it can form by drying this.
A polymerizable monomer or oligomer may be used as the binder resin, dissolved in a solvent and coated, and then crosslinked or polymerized. If necessary, for example, an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, an electron transporting substance, and a filler may be added.
Examples of the solvent used in the coating solution for each layer of the single layer type photosensitive layer or the multilayer type photosensitive layer include, for example, alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, halogenated carbonization. Examples thereof include hydrogen solvents and aromatic solvents.
Specific examples include water, methanol, ethanol, n-propanol, isopropanol, butanol, methyl cellosolve, methoxypropanol, dimethylformamide, dimethylacetamide, and dimethylsulfoxide. Examples include acetone, methyl ethyl ketone, cyclohexanone, diethyl ether, dipropyl ether, propylene glycol monomethyl ether, dioxane, methylal, and tetrahydrofuran.
Further, methyl acetate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, chlorobenzene, dichloromethane, chloroform, trichloroethylene, tetrachloroethylene, carbon tetrachloride, benzene, toluene, xylene and tetralin can be mentioned. These solvents can be used alone or in combination of two or more.
As a method for applying the coating liquid for each of the above layers, for example, a dip coating method (dip coating method), a spray coating method, or a spinner coating method can be used. Also, a roller coating method, a Meyer bar coating method, and a blade coating method can be used.
<Configuration of electrophotographic apparatus>
FIG. 5 shows an example of an electrophotographic image forming apparatus according to the present invention. In FIG. 5, a cylindrical electrophotographic photosensitive member 501 is rotationally driven with a predetermined peripheral speed (process speed) in the direction of an arrow about an axis 502. Around the electrophotographic photosensitive member 501, an image forming unit for forming an electrostatic latent image on the surface of the electrophotographic photosensitive member 501 is disposed.
Specifically, a charging unit (primary charging unit) 503 and an exposure unit (image exposure unit) are arranged along the rotation direction of the photoconductor 501. More specifically, the photoconductor 501 is uniformly charged to a predetermined potential (negative polarity in this example) by a charging roller that functions as a charging unit, and then functions as an exposure unit based on image information of a document. The laser (image exposure light) 504 emitted from the laser beam is received. In this way, an electrostatic latent image corresponding to target image information is formed on the surface of the electrophotographic photosensitive member 501.
In this example, the effect is particularly great when charging means using discharge is used. The electrostatic latent image formed on the surface of the electrophotographic photosensitive member 501 is then developed (reversed development in this example) with a negatively charged toner (indeterminate toner or spherical toner) in the developing means 505 to form a toner image. It is formed. At this time, the particle diameter of the toner is preferably 3 to 10 μm.
The toner image formed on the surface of the electrophotographic photosensitive member 501 is transferred onto a transfer material by a transfer bias from a transfer unit (transfer roller in this example) 506. At this time, the transfer material (sheet, recording material) 509 is synchronized with the rotation of the electrophotographic photoreceptor 501 between the electrophotographic photoreceptor 501 and the transfer means 506 (contact portion) from a transfer material supply means (not shown). Then, it is taken out and fed. At this time, from the viewpoint of improving transferability, a speed difference may be provided between the rotation of the electrophotographic photosensitive member 501 and the moving speed of the transfer means.
Further, a bias voltage having a polarity opposite to the charge held in the toner is applied to the transfer means from a bias power source (not shown). Further, the transfer unit 506 performs primary transfer for transferring a toner image from the electrophotographic photosensitive member 501 to an intermediate transfer member (not shown) and transfer from the intermediate transfer member (not shown) to form an image of a secondary color or higher. A two-stage configuration including secondary transfer to be transferred to the material 509 may be used.
The transfer material 509 on which the toner image has been transferred is separated from the surface of the electrophotographic photosensitive member, conveyed to the fixing means 508, and subjected to a fixing process of the toner image, whereby an electrophotographic apparatus is formed as an image formed product (print, copy). Printed out.
The surface of the electrophotographic photosensitive member 501 after the transfer of the toner image has a cleaning member (in this example, a blade counter-contacted with the photosensitive member) disposed in contact with (in contact with) the surface of the electrophotographic photosensitive member 501. In step 507, the surface is cleaned by removing deposits such as transfer residual toner. Further, after being subjected to charge removal processing by pre-exposure light (not shown) from a pre-exposure means (not shown), it is repeatedly used for image formation. Note that pre-exposure is not always necessary.
Among the components selected from the image forming process equipment such as the electrophotographic photosensitive member 501, the charging unit 503, the developing unit 505, and the cleaning unit 507, a plurality of components are housed in a container and combined as a process cartridge (cartridge) PC. You may comprise. Further, the process cartridge PC can be configured to be detachable from an apparatus main body of an electrophotographic apparatus such as a copying machine or a laser beam printer.
That is, at least the electrophotographic photosensitive member 501 and a cleaning unit 507 having a cleaning member disposed in contact with the electrophotographic photosensitive member are integrally supported, and the process cartridge PC is configured to be detachable from the main body of the electrophotographic apparatus. . The electrophotographic apparatus having the process cartridge PC and using at least pseudo halftone processing formed with dots as a method of expressing gradation can be configured.
The exposure light 504 is reflected light or transmitted light from the original when the electrophotographic apparatus is a copying machine or a printer. Alternatively, a document is read by a sensor, or electronic data generated by an information device such as a personal computer is converted into a signal, and light emitted by, for example, scanning a laser beam or driving an LED array or a liquid crystal shutter array is performed according to this signal. It is. The image forming apparatus (electrophotographic apparatus) of the present example uses a pseudo halftone process formed of at least dots as a technique for expressing gradation in signal conversion.
The electrophotographic image forming apparatus according to the present invention can generate a pseudo halftone process formed of dots using a dither matrix at the time of signalization. FIG. 16 is an example of a dot concentration type dither matrix. If this dither matrix is used, 256 gradations can be expressed by a dot pattern of 1200 dpi, 106 lpi, and 45 degrees. Specifically, the input multi-valued image data represented by 0 to 255 is compared with the numerical value (threshold value) in the dither matrix of FIG. 16, and if it is larger than the threshold value, black is printed (printed). For example, it is replaced with white (not printed) and converted to a binary image.
The resolution used in recent electrophotographic apparatuses is mainly 600 dpi to 2400 dpi. In many cases, the number of lines is 106 to 212 lpi. Also, since black has high visibility, the screen angle is often set at 45 degrees where the visibility is angularly degraded. In the embodiment, an AM screening pattern is used as the pseudo halftone process, and a 45 degree square pattern of 106 lpi that can be formed even at 600 dpi and a 45 degree square pattern of 212 lpi (adjacent dot angle is 90 degrees) are used.
In the case of a so-called tandem system in which the image forming apparatus is provided with a photoconductor and an image forming unit for each toner color, the configuration of this example may be adopted for at least one image forming station. It ’s fine. For example, in an image forming apparatus of a tandem system, a heater is installed in the photosensitive body in an image forming station that forms a black image, and the configuration of this example is not adopted in this image forming station, and toner images of other colors are used. The image forming station to be formed may be an image forming apparatus adopting the configuration of this example.

Hereinafter, the present invention will be described in more detail with reference to specific examples. In the examples, “part” means “part by mass”. Further, the electrophotographic photoreceptor is hereinafter simply referred to as “photoreceptor”. In all the following examples, the shape of the opening of the recess formed on the surface of the electrophotographic photosensitive member is a circular shape in which the longest diameter of the opening and the shortest diameter of the opening are substantially equal.
(Production example of photoreceptor A before formation of recesses)
An aluminum cylinder having a diameter of 30.52 mm and a length of 370 mm was used as a support (cylindrical support).
Next, zinc oxide particles (specific surface area: 19 m as metal oxide) ² / G, powder resistance: 4.7 × 10 ⁶ 100 parts of (Ω · cm) were stirred and mixed with 500 parts of toluene. To this, 0.8 part of a silane coupling agent (compound name: N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, trade name: KBM602, manufactured by Shin-Etsu Chemical Co., Ltd.) is added for 6 hours. Stir. Thereafter, toluene was distilled off under reduced pressure, followed by heating and drying at 130 ° C. for 6 hours to obtain surface-treated zinc oxide particles.
Next, 15 parts of butyral resin (trade name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) and 15 parts of blocked isocyanate (trade name: Sumijoule 3175, manufactured by Sumitomo Bayern Urethane Co., Ltd.) as a polyol resin are mixed solution. Dissolved. The mixed solution is a mixture of 73.5 parts of methyl ethyl ketone and 73.5 parts of 1-butanol.
To this solution, 80.8 parts of the surface-treated zinc oxide particles and 0.8 part of 2,3,4-trihydroxybenzophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, and this was added to a glass having a diameter of 0.8 mm. Dispersion was performed in a sand mill apparatus using beads in an atmosphere of 23 ± 3 ° C. for 3 hours. After the dispersion, the following two substances were added and stirred to prepare an undercoat layer coating solution.
・ Silicone oil (trade name: SH28PA, manufactured by Toray Dow Corning Silicone)
... 0.01 parts
Cross-linked polymethyl methacrylate (PMMA) particles (trade name: TECHPOLYMERSSX-102, manufactured by Sekisui Plastics Co., Ltd., average primary particle size 2.5 μm)
... 5.6 parts
This undercoat layer coating solution was applied onto the support by dip coating, and the resulting coating film was dried at 160 ° C. for 40 minutes to form an undercoat layer having a thickness of 18 μm.
Next, the following four substances were placed in a sand mill using glass beads having a diameter of 1 mm, dispersed for 4 hours, and then 700 parts of ethyl acetate was added to prepare a charge generation layer coating solution.
-Crystal form hydroxygallium phthalocyanine crystal (charge generating material) with strong peaks at 7.4 ° and 28.2 ° with Bragg angle 2θ ± 0.2 ° in CuKα characteristic X-ray diffraction 20 parts
-Calixarene compound represented by the following structural formula (A): 0.2 part
・ Polyvinyl butyral (trade name: ESREC BX-1, manufactured by Sekisui Chemical Co., Ltd.)
... 10 copies
・ Cyclohexanone: 600 parts
The charge generation layer coating solution was dip-coated on the undercoat layer, and the resulting coating film was dried at 80 ° C. for 15 minutes to form a charge generation layer having a thickness of 0.17 μm.
Next, a charge transport layer coating solution was prepared by dissolving the following five substances in a mixed solvent of 600 parts of mixed xylene and 200 parts of dimethoxymethane.
・ Compound represented by the following structural formula (B) (charge transport material) 30 parts
・ Compound represented by the following structural formula (C) (charge transport material): 60 parts
-Compound represented by the following structural formula (D): 10 parts
・ Polycarbonate resin (trade name: Iupilon Z400, manufactured by Mitsubishi Engineering Plastics Co., Ltd., bisphenol Z type polycarbonate) ・ ・ ・ 100 parts
-Polycarbonate represented by the following structural formula (E) (viscosity average molecular weight Mv: 20000)
... 0.02 parts
The charge transport layer coating solution was dip-coated on the charge generation layer, and the resulting coating film was dried at 115 ° C. for 30 minutes to form a charge generation layer having a thickness of 18 μm.
Next, a mixed solvent of 20 parts of 1,1,2,2,3,3,4-heptafluorocyclopentane (trade name: Zeolora H, manufactured by Nippon Zeon Co., Ltd.) / 20 parts of 1-propanol was added to polyflon. The mixture was filtered with a filter (trade name: PF-040, manufactured by Advantech Toyo Co., Ltd.). The following three substances were added to this mixed solvent. By filtering this with a polyflon filter (trade name: PF-020, manufactured by Advantech Toyo Co., Ltd.), a coating solution for a second charge transport layer (protective layer) was prepared.
・ Hole transporting compound represented by the following structural formula (F): 90 parts
・ 1,1,2,2,3,3,4-heptafluorocyclopentane 70 parts
・ 1-propanol: 70 parts
The coating solution for the second charge transport layer was dip-coated on the charge transport layer, and the obtained coating film was dried at 50 ° C. for 6 minutes in the air. Thereafter, in nitrogen, the coating film was irradiated with an electron beam for 1.6 seconds under the conditions of an acceleration voltage of 70 kV and an absorbed dose of 8000 Gy while rotating the support (object to be irradiated) at 200 rpm.
Subsequently, the temperature was raised from 25 ° C. to 125 ° C. over 30 seconds in nitrogen, and the coating film was heated. The oxygen concentration in the atmosphere during electron beam irradiation and subsequent heating was 15 ppm. Next, the second charge transport layer (protective layer) having a thickness of 5 μm was formed by performing a heat treatment at 100 ° C. for 30 minutes in the air.
As described above, a photoreceptor A, which is an electrophotographic photoreceptor before forming a recess on the surface, was produced. The surface of the photoreceptor A was observed, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated for SCR1 and SCR2, which will be described later. The results are shown in Table 2.
(Production example of photoreceptor B before formation of recesses)
In the production example of photoconductor A, before forming a recess on the surface in the same manner as in the photoconductor A production example, except that an aluminum cylinder having a diameter of 84 mm and a length of 370 mm was used as the support (cylindrical support). A photoconductor B which is an electrophotographic photoconductor was prepared.
The surface of the photoreceptor B was observed, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated for SCR1 and SCR2, which will be described later. The results are shown in Table 2.
(Production example of photoreceptor C before formation of recess)
In the same manner as in the photoconductor A production example, a conductive layer, an undercoat layer, a charge generation layer, and a charge transport layer were formed on a support. Next, a lubricant dispersion was obtained by the following procedure.
Fluorine atom-containing resin (trade name: GF-300, manufactured by Toagosei Co., Ltd.) 0.5 part as a dispersant was dissolved in the following mixed solvent.
・ 1,1,2,2,3,3,4-heptafluorocyclopentane (trade name: Zeolora H, manufactured by Nippon Zeon Co., Ltd.) 30 parts
・ 1-propanol: 30 parts
To this, 10 parts of polytetrafluoroethylene (trade name: Lubron L-2, manufactured by Daikin Industries, Ltd.) as a lubricant was added. This is put into a high-pressure disperser (trade name: Microfluidizer M-110EH, manufactured by Microfluidics, USA), and 600 kgf / cm. ² The dispersion treatment was performed four times at the pressure of This was filtered with a polyflon filter (trade name: PF-040, manufactured by Advantech Toyo Co., Ltd.) to obtain a lubricant dispersion.
Thereafter, 90 parts of the hole transporting compound represented by the structural formula (F), 70 parts of 1,1,2,2,3,3,4-heptafluorocyclopentane, and 70 parts of 1-propanol were lubricated. It was added to the agent dispersion. By filtering this with a polyflon filter (trade name: PF-020, manufactured by Advantech Toyo Co., Ltd.), a coating solution for a second charge transport layer (protective layer) was prepared.
The coating solution for the second charge transport layer was dip-coated on the charge transport layer, and the obtained coating film was dried at 50 ° C. for 6 minutes in the air. Thereafter, in nitrogen, the coating film was irradiated with an electron beam for 1.6 seconds under the conditions of an acceleration voltage of 70 kV and an absorbed dose of 8000 Gy while rotating the support (object to be irradiated) at 200 rpm. Subsequently, the temperature was raised from 25 ° C. to 125 ° C. over 30 seconds in nitrogen, and the coating film was heated. The oxygen concentration in the atmosphere during electron beam irradiation and subsequent heating was 15 ppm. Next, the second charge transport layer (protective layer) having a thickness of 5 μm was formed by performing a heat treatment at 100 ° C. for 30 minutes in the air.
As described above, Photoconductor C, which is an electrophotographic photoconductor before forming a recess on the surface, was produced. The surface of the photoreceptor C was observed, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated for SCR1 and SCR2, which will be described later. The results are shown in Table 2.
(Manufacturing example of the photoreceptor D before forming the recess)
In the same manner as in the photoconductor A production example, a conductive layer, an undercoat layer, a charge generation layer, and a charge transport layer were formed on a support. Next, a coating solution for the second charge transport layer (protective layer) was prepared by the following procedure.
The following mixture is put into a high-pressure disperser (trade name: Microfluidizer M-110EH, manufactured by Microfluidics), and 600 kgf / cm. ² The dispersion treatment was performed three times at a pressure of
Alumina particles (average particle size: 0.1 μm, trade name: LS-231, manufactured by Nippon Light Metal Co., Ltd.) ... 10 parts
・ Chlorobenzene: 90 parts
Furthermore, the dispersion liquid subjected to the dispersion treatment was filtered with a polyflon filter (trade name: PF-040, manufactured by Advantech Toyo Co., Ltd.) to prepare a dispersion liquid. And
-Compound having the structure represented by the structural formula (C) 70 parts
・ Polycarbonate (trade name: Iupilon Z400, manufactured by Mitsubishi Engineering Plastics) ... 100 parts
・ The above dispersion liquid: 200 parts
・ Monochlorobenzene: 400 parts
・ Dimethoxymethane: 200 parts
Were mixed to prepare a coating solution for the second charge transport layer (protective layer).
The coating solution for the second charge transport layer is spray-coated on the charge transport layer, and the obtained coating film is dried at 130 ° C. for 20 minutes to form a second charge transport layer (protective layer) having a thickness of 5 μm. did.
As described above, a photoconductor D, which is an electrophotographic photoconductor before forming a recess on the surface, was produced. The surface of the photoreceptor D was observed, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated for SCR1 and SCR2, which will be described later. The results are shown in Table 2.
(Production example of photoconductor E)
A conductive layer, an undercoat layer, a charge generation layer, and a charge transport layer were formed on the support in the same manner as in the production example of the photoreceptor A before forming the recess. Next, a coating solution for the second charge transport layer (protective layer) was prepared by dissolving the following substances in 20.9 parts of 1-methoxy-2-propanol.
・ Acrylic polyol (trade name: JONCRYL-587, manufactured by Johnson Polymers) 1.5 parts
Melamine resin (trade name: CYMEL-303, manufactured by Cytec Industries)
... 2.1 parts
N, N, N ′, N′-tetrakis-[(4-hydroxymethyl) phenyl] -biphenyl-4,4′-diamine (THM-TBD) as a charge transport component
... 1.16 parts
-N, N'-diphenyl-N, N'-di (3-hydroxyphenyl) -terphenyl-diamine (DHTER) as a charge transport component ... 1.93 parts
・ Acid catalyst (trade name: Nacure 5225, manufactured by King Chemical Industries) 0.05 parts
This second charge transport layer coating solution was dip coated on the charge transport layer and thermally cured at 140 ° C. for 40 minutes to form a second charge transport layer (protective layer) having a thickness of 6 μm.
The photoreceptor E was produced as described above. The surface of the photoreceptor E was observed by the above-described method, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated for SCR1 and SCR2, which will be described later. The results are shown in Table 2.
(Formation of recesses by mold pressure transfer)
In the press-fitting shape transfer processing apparatus having a configuration generally shown in FIG. 4, a mold having a convex shape was installed, and surface processing was performed on the electrophotographic photosensitive member before forming the concave portion.
A mold having a convex shape is shown in FIG. In the embodiment, the regularly arranged mold shown in FIG. 6A and the irregularly arranged mold shown in FIG. 6B were used. In FIG. 6, Xm is the longest diameter of the convex part (the longest diameter when the convex part on the mold is viewed from above; the same applies hereinafter), and θ is the main scanning direction of exposure light in a square arrangement (horizontal direction in FIG. 6). ), And H represents the height of the convex portion. The mold was produced as follows.
First, the arrangement of the convex portions was designed. In the following description of the layout design, the area and area ratio indicate the area and area ratio when the convex portion on the mold is viewed from above.
FIG. 6A shows a square arrangement in which Y1 and Y2 are equally spaced. For the design of the square arrangement, a conversion method from Adobe Photoshop's gray scale to monochrome two gradations (halftone screen) was used.
First, a gray scale having a density corresponding to the area ratio of the convex portion to be designed is created. For example, when the area ratio of the convex portion is desired to be 20%, a gray scale having a density of 20% is created. Next, in monochrome two-tone conversion, change the dot shape to a circle, set the number of lines (distance between Y1 and Y2) calculated from the longest diameter Xm and area ratio to be designed, and the angle θ and convert it to a halftone screen. did. When the resolution was insufficient, the coordinates of the arrangement were extracted from the obtained halftone screen, and the convex portions with the longest diameter Xm were rearranged. A square arrangement was created as described above.
FIG. 6B shows an irregular arrangement by the above-described Floyd-Steinberg method. First, a gray scale having a density corresponding to the area ratio of the convex portion to be designed is created. Next, a square having the same area as that of one convex portion having the longest diameter Xm is set as a unit pixel, and binarization is performed using a distribution rule shown in FIG. Generated irregular pattern. At this time, only the first pixel was set to the density of the 255th gradation, and the calculation was started. Next, in the binarized irregular pattern, an irregular arrangement was created by arranging convex portions having the longest diameter Xm in pixels corresponding to the pattern.
FIG. 6C shows a checker mark-like square in which square arrangement areas A in which Y1 and Y2 are equally spaced and square arrangement areas B in which Y3 and Y4 are equally spaced are arranged alternately every 500 μm square. Arrangement. Xm in the region A and Xn in the region B, Y1 (Y2) in the region A, and Y3 (Y4) in the region B were designed with different sizes.
FIG. 6D shows a square arrangement in which the longest diameter is staggered, in which Xm is alternately replaced with Xn after the square arrangement of FIG. 6A is performed.
Electronic data was created by adding the height H of the convex portion to the convex portion arrangement designed as described above. Although the three-dimensional shape of the convex portion can be arbitrarily selected, a circular dome shape is adopted in the embodiment. The resist is irradiated with light based on the created electronic data, creating a convex shape, creating a mold that is inverted, and subsequently electroforming nickel to create a nickel mold having a convex shape .
Various molds were prepared by changing Xm, Xn, Y1 (Y2), Y3 (Y4), H, and θ by the above method.
At the time of surface processing, the temperature of the electrophotographic photosensitive member and the mold is controlled so that the surface temperature of the electrophotographic photosensitive member becomes a predetermined temperature, and the electrophotographic photosensitive member and the pressure member are pressed at a desired pressure while performing electrophotography. The photoreceptor is rotated in the circumferential direction. Thereby, a concave portion was formed on the entire surface (circumferential surface) of the electrophotographic photosensitive member. As described above, an electrophotographic photosensitive member having a concave portion on the surface was prepared.
(Observation of the surface of the electrophotographic photoreceptor)
The surface of the electrophotographic photosensitive member having a concave portion on the surface is enlarged and observed with a laser microscope (manufactured by Keyence Corporation, trade name: VK-9500) with a 10 to 50 times lens, and the electrophotographic photosensitive member is as described above. The specific recessed part and flat part provided in the surface of this were determined.
At the time of observation, adjustment was performed so that there is no inclination in the longitudinal direction of the electrophotographic photosensitive member, and the circumferential direction was focused on the apex of the arc of the electrophotographic photosensitive member. A square region having a side of 500 μm was obtained by connecting the enlarged images with an image connection application. Moreover, about the obtained result, image processing height data was selected with attached image analysis software, and the filter process was performed by the filter type median. Based on the above observation, the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined.
In addition, the surface of the electrophotographic photosensitive member having a concave portion on the surface was observed by the same method as described above using another laser microscope (trade name: X-200, manufactured by Keyence Corporation). In this case, the same result as that obtained when the above laser microscope (manufactured by Keyence Corporation, trade name: VK-9500) was used was obtained. In the following examples, a laser microscope (manufactured by Keyence Co., Ltd., trade name: VK-9500) and a 50 × lens were used for observing an electrophotographic photoreceptor having a concave portion on the surface.
(Calculation of image quality degradation index)
The electrophotographic photosensitive member having a concave portion on the surface was observed with a CCD camera using GX-700 manufactured by Rebox Co., Ltd., and photographic data in a square region having a side of 10.84 mm was obtained. The binarization process was performed on the acquired image to acquire the coordinates of the concave portion arrangement. Next, the opening shape of the specific recesses obtained by laser microscope observation was reflected in the coordinates of the recess arrangement, and the arrangement of multiple recesses (A) was made.
In addition, when the mold is observed using the laser microscope, and the outer peripheral shape of the convex portion of the mold matches the opening shape of the specific concave portion that was observed earlier, the convex portion arrangement used when creating the mold is used. This electronic data was taken as the arrangement (A) of a plurality of recesses.
As the screen pattern (B), the following two were created using a conversion method from Adobe Photoshop's gray scale to monochrome 2 gradation (halftone screen).
-Square layout screen pattern 1 (SCR1) with a circular dot shape, line number 106 lpi, angle 45 °, printing rate 40%
-Square layout screen pattern 2 (SCR2) with a circular dot shape, 212 lpi line, 45 ° angle, 40% printing rate
The image quality degradation index was calculated according to the calculation method described above using the plurality of concave portion arrangements (A) and screen patterns (B) obtained above. Adobe (Photoshop) was used to create the image (C). For particle analysis, Keyence Corporation particle analysis software (GRADING ANALYSIS) VH-H1G1 was used.
(Image quality evaluation 1)
The electrophotographic photosensitive member having a concave portion on the surface is mounted on a cyan station of a modified machine of an electrophotographic apparatus (copier) (trade name: iR-ADV C7065) manufactured by Canon Inc., and evaluated as follows. It was.
First, in a 23 ° C./50% RH environment, the charging device and the image exposure are performed so that the dark potential (Vd) of the electrophotographic photosensitive member is −700 V, the bright potential (Vl) is −200 V, and the developing potential is −540 V. The conditions of the apparatus and the developing apparatus were set.
The dither matrix set to cyan in the electrophotographic apparatus was changed to a dither matrix having a line number of 106 lpi, an angle of 45 °, and a resolution of 1200 dpi.
A gray scale with a density of 40% was created in A4 size using Adobe Photoshop. By outputting via a printer driver, halftone 1 (HT1) composed of screen pattern 1 (SCR1) having a line number of 212 lpi, an angle of 45 °, and a printing rate of 40% was obtained. The obtained halftone 1 (HT1) was ranked by visual evaluation similar to the image quality evaluation 1.
Halftone 1 (HT1) was ranked by visual evaluation compared to the limit sample. The limit sample is composed of 20 halftone images having different image quality degradation levels, which are output using a halftone image having no image quality degradation and an electrophotographic photosensitive member having a recess on the surface, with 20 electrophotographic device developers as subjects. Were set in comparison. The contents of the limit sample are shown below.
A: Image that all subjects judged that the image quality did not deteriorate
B: Image with different judgments as to whether or not the roughness is reduced by the subject
C: An image with different judgments as to whether or not the moire has been reduced by the subject.
D: The best image among all the images judged by all the subjects to be less crisp
E: The best image among all the images judged by all the subjects to have reduced moire
In this example, A to C are acceptable image quality degradation.
(Image quality evaluation 2)
In the image output of image quality evaluation 1, the dither matrix set to cyan in the electrophotographic apparatus was changed to a dither matrix having a line number of 212 lpi, an angle of 45 °, and a resolution of 1200 dpi. A gray scale with a density of 40% was created in A4 size using Adobe Photoshop. By outputting via a printer driver, halftone 2 (HT2) composed of screen pattern 2 (SCR2) having a line number of 212 lpi, an angle of 45 °, and a printing rate of 40% was obtained. The obtained halftone 2 (HT2) was ranked by visual evaluation similar to the image quality evaluation 1.
(Image quality evaluation 3)
An electrophotographic photosensitive member having a concave portion on the surface is mounted on a black station of a modified machine of an electrophotographic apparatus (copier) (trade name: iR-ADV C7065) manufactured by Canon Inc., and evaluated as follows. It was.
First, in a 23 ° C./50% RH environment, the charging device and the image exposure are performed so that the dark potential (Vd) of the electrophotographic photosensitive member is −700 V, the bright potential (Vl) is −200 V, and the developing potential is −540 V. The conditions of the apparatus and the developing apparatus were set.
The dither matrix set to black in the electrophotographic apparatus was changed to a dither matrix having a line number of 106 lpi, an angle of 45 °, and a resolution of 1200 dpi. A gray scale with a density of 40% was created in A4 size using Adobe Photoshop. By outputting via a printer driver, halftone 3 (HT3) composed of screen pattern 1 (SCR1) having a line number of 212 lpi, an angle of 45 °, and a printing rate of 40% was obtained. The obtained halftone 3 (HT3) was ranked by visual evaluation similar to the image quality evaluation 1.
(Image quality evaluation 4)
An electrophotographic photosensitive member having a concave portion on the surface is mounted on a black station of a modified machine of an electrophotographic apparatus (copier) (trade name: iR-ADV C7065) manufactured by Canon Inc., and evaluated as follows. It was.
First, in a 23 ° C./50% RH environment, the charging device and the image exposure are performed so that the dark potential (Vd) of the electrophotographic photosensitive member is −700 V, the bright potential (Vl) is −200 V, and the developing potential is −540 V. The conditions of the apparatus and the developing apparatus were set.
A gray scale with a density of 40% was created in A4 size by Adobe Photoshop and output via a printer driver. Halftone 4 composed of screen pattern 2 (SCR2) with a line number of 212 lpi, an angle of 45 °, and a print rate of 40% by selecting halftone: resolution and resolution: 1200 dpi in the printer driver settings. (HT4) was obtained. The obtained halftone 4 (HT4) was ranked by visual evaluation similar to the image quality evaluation 1.
(Image flow evaluation 1)
A photoreceptor having a concave portion on the surface was mounted on a cyan station (contact charging method) of a modified machine of an electrophotographic apparatus (copier) (trade name: iR-ADV C7055) manufactured by Canon Inc.
First, in an environment of 30 ° C./80% RH, the charging device and image exposure are performed so that the dark portion potential (Vd) of the electrophotographic photosensitive member is −700 V, the light portion potential (Vl) is −200 V, and the development potential is −540 V. The conditions of the apparatus and the developing apparatus were set. The dither matrix was changed to that used for image quality evaluation.
Next, as shown in Table 2, a polyurethane rubber cleaning blade having a hardness of 77 ° was set so that the contact angle with respect to the surface of the electrophotographic photosensitive member was 28 ° and the contact pressure was 15 g / cm. With the heater (drum heater) for the electrophotographic photosensitive member turned off, 50000 continuous evaluation charts for images with a 5% A4 printing ratio were output in an environment of 30 ° C./80% RH.
Subsequently, with the heater (drum heater) for the electrophotographic photosensitive member turned off, an evaluation chart for an image with a 5% A4 horizontal printing rate is output continuously in an environment of 30 ° C./80% RH. The sample was left for 3 days in a 30 ° C./80% RH environment with the power off.
After being left for 3 days, the electrophotographic apparatus was started up, and an image of 1 dot-1 space with an A4 horizontal output resolution of 600 dpi was formed, and the image density in the vicinity of the charging device and the image reproducibility of the entire A4 were evaluated as follows. .
A: In the vicinity of the charging device, there is no dot disturbance or scattering (that is, no image flow), and the image reproducibility is good.
B: In the vicinity of the charging device, a slight dot disturbance is observed when magnified, but there is no scattering, and the image reproducibility is good for other portions.
C: In the vicinity of the charging device, the dots are slightly disturbed or scattered when magnified, but the image reproducibility is good for other portions.
D: Disturbance and scattering of dots occur in the vicinity of the charging device when magnified, but the image reproducibility is good for other portions.
E: Whitening occurs on the image in the vicinity of the charging device, and the image reproducibility is slightly low in other portions.
(Image flow evaluation 2 to 10)
Except for the hardness and setting (contact angle and contact pressure) of the cleaning blade as shown in Table 3, the actual evaluation of the electrophotographic photosensitive member was performed in the same manner as the image flow evaluation 1 of the photosensitive member having a concave portion on the surface. went.
(Image Flow Evaluation 11-20)
A photoconductor having a concave portion on the surface was mounted on a black station (corona charging system) of a modified machine of an electrophotographic apparatus (copier) (trade name: iR-ADV C7055) manufactured by Canon Inc. Except for the hardness and setting (contact angle and contact pressure) of the cleaning blade as shown in Table 4, the actual evaluation of the electrophotographic photosensitive member was performed in the same manner as the image flow evaluation 1 of the photosensitive member having a recess on the surface. went.
(Production Example 1 of electrophotographic photosensitive member having a recess on the surface)
Using the electrophotographic photosensitive members A, B, C, and D before the formation of the recesses, the recesses are formed by mold press-contact shape transfer using the square arrangement mold shown in FIG. Photoconductors AA-1 to 40, BA-1 to 3, CA-1, and DA-1 were prepared. Table 5 shows the mold used for the pressure contact shape transfer and the surface temperature of the electrophotographic photosensitive member during surface processing.
The surface of these electrophotographic photoreceptors was observed by the above-described method, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated. As the screen pattern (B), the above-described screen pattern 1 (SCR1) and screen pattern 2 (SCR2) were used. The results are shown in Table 5.
Further, when the cross section of the vicinity of the second charge transport layer, which is the surface layer of the electrophotographic photosensitive member CA-1, was observed, as shown in FIG. 8A, not only the surface of the second charge transport layer. Also, a concave portion corresponding to the surface of the charge transport layer (interface between the charge transport layer and the second charge transport layer) was formed. A concave portion as shown in FIG. 8B was formed on the surface of the electrophotographic photosensitive member CA-1. A white line rectangle in FIG. 8B is a square region having a side of 500 μm.
(Production Example 2 of electrophotographic photosensitive member having a recess on the surface)
Using the electrophotographic photoreceptors A, B, C, and D before the formation of the recesses, the irregularly placed mold shown in FIG. 6B is used to form the recesses by mold press-fitting shape transfer, and the electrons having the recesses on the surface. Photoconductors AB-1 to 40, BB-1, CB-1, and DB-1 were prepared. Table 6 shows the mold used for the pressure contact shape transfer and the surface temperature of the electrophotographic photosensitive member during surface processing.
These electrophotographic photosensitive members are observed in the same manner as in Production Example 1 of the electrophotographic photosensitive member having a concave portion on the surface, and the depth of the specific concave portion, the longest diameter and area of the opening portion, the area of the flat portion, and the arrangement of the concave portion The image quality degradation index (f) was calculated. The results are shown in Table 6.
(Production Example 3 of Electrophotographic Photoreceptor Having Recessed Surface)
Using the electrophotographic photosensitive member A before forming the concave portion, using the mold having the arrangement shown in FIGS. 6C and 6D, the concave portion is formed by mold pressure contact shape transfer, and the surface has the concave portion. AC-1 and AD-1 were prepared. Table 7 shows the mold used for pressure contact shape transfer and the surface temperature of the electrophotographic photosensitive member during surface processing.
These electrophotographic photosensitive members are observed in the same manner as in Production Example 1 of the electrophotographic photosensitive member having a concave portion on the surface, and the depth of the specific concave portion, the longest diameter and area of the opening portion, the area of the flat portion, and the arrangement of the concave portion The image quality degradation index (f) was calculated. The results are shown in Table 7.
(Production Example 4 of Electrophotographic Photoreceptor Having Recessed Surface)
A conductive layer, an undercoat layer, a charge generation layer, and a charge transport layer were formed on the support in the same manner as in the production example of the photoreceptor A before forming the recess. Next, the following substances were dissolved in 20.9 parts of 1-methoxy-2-propanol to prepare a coating solution for the second charge transport layer (protective layer).
・ Acrylic polyol (trade name: JONCRYL-587, manufactured by Johnson Polymers) 1.5 parts
Melamine resin (trade name: CYMEL-303, manufactured by Cytec Industries)
... 2.1 parts
N, N, N ′, N′-tetrakis-[(4-hydroxymethyl) phenyl] -biphenyl-4,4′-diamine (THM-TBD) as a charge transport component
... 1.16 parts
-N, N'-diphenyl-N, N'-di (3-hydroxyphenyl) -terphenyl-diamine (DHTER) as a charge transport component ... 1.93 parts
・ Acid catalyst (trade name: Nacure 5225, manufactured by King Chemical Industries) 0.05 parts
Prior to curing the coating film obtained by dip-coating the coating solution for the second charge transport layer on the charge transport layer, the surface temperature of the coating film was set to room temperature (25 The shape of the mold was transferred to the surface of the coating film while being maintained at (° C.). Next, a second charge transport layer (protective layer) having a film thickness of 6 μm was formed by thermosetting at 140 ° C. for 40 minutes.
As described above, electrophotographic photoreceptors EA-1 and EB-1 having concave portions on the surface were produced. Tables 8 and 9 show the mold used for the pressure contact shape transfer and the surface temperature of the electrophotographic photosensitive member during surface processing.
These electrophotographic photosensitive members are observed in the same manner as in Production Example 1 of the electrophotographic photosensitive member having a concave portion on the surface, and the depth of the specific concave portion, the longest diameter and area of the opening portion, the area of the flat portion, and the arrangement of the concave portion The image quality degradation index (f) was calculated. The results are shown in Tables 8 and 9.
In Production Examples 1 to 4 of the electrophotographic photosensitive member having a concave portion on the surface, the case where the shape (size / depth) of the concave portion formed on the surface of the photosensitive member is almost uniform will be described as an example. However, the following example is also acceptable. That is, as long as moire is not visually recognized, for example, an excessively large recess may be slightly formed due to a flare or the like during manufacture.
(Production Example 5 of electrophotographic photosensitive member having a concave portion on the surface)
A dry blasting process is performed on the photoreceptor A before forming the recesses by using a dry blasting apparatus having a configuration shown in FIG. 9 so that a plurality of dimple-shaped recesses are formed on the entire surface (peripheral surface) of the electrophotographic photoreceptor. Formed.
In FIG. 9, reference numeral 901 denotes an injection nozzle for particles (abrasive particles) 905. Reference numeral 902 denotes a nozzle fixing jig for fixing the injection nozzle 901. Reference numeral 903 denotes an air (compressed air) introduction path. Reference numeral 904 denotes a path for guiding particles (abrasive particles) 905 stored in the container to the injection nozzle 901. Reference numeral 905 denotes particles (abrasive particles). Reference numeral 906 denotes a work support member for supporting the work 907. Reference numeral 907 denotes a work (an electrophotographic photosensitive member on which a concave portion is formed on the surface). Reference numeral 908 denotes an injection nozzle support member for supporting the injection nozzle 901. Reference numeral 909 denotes an injection nozzle fixing jig for fixing the injection nozzle 901.
As described above, an electrophotographic photosensitive member P having a concave portion on the surface was produced. The conditions for the dry blast treatment are as follows. After dry blasting, particles (abrasive particles) remaining on the peripheral surface of the workpiece were removed by blowing compressed air.
Particles (abrasive particles): spherical glass beads with an average particle size of 30 μm (trade name: UB-01L, manufactured by Union)
・ Air (compressed air) spraying pressure: 0.343 MPa (3.5 kgf / cm ² ) Injection nozzle moving speed: 430 mm / s (up and down arrow direction in FIG. 9)
・ Work rotation speed: 288 rpm (in the direction of the rotation arrow in FIG. 9)
・ Distance between discharge port of injection nozzle and workpiece: 100mm
・ Discharge angle of particles (abrasive particles): 90 °
-Supply amount of particles (abrasive particles): 200 g / min
・ Blasting frequency: One way x 2 times
The electrophotographic photosensitive member P is observed in the same manner as in Production Example 1 of the electrophotographic photosensitive member having a concave portion on the surface, and the depth of the specific concave portion, the longest diameter and area of the opening portion, the area of the flat portion, and the arrangement of the concave portion are determined. The image quality degradation index (f) was calculated. The results are shown in Table 10.
(Examples 1-42)
The above-mentioned image quality evaluation 1 was performed on the photoreceptors AA-8 to 15, 18 to 20, 22 to 24, 28, 29, 31, 32, and 35 having concave portions on the surface. Further, the photoreceptors AB-8, 9, 12-15, 18-20, 22-24, 28, 29, 31, 32, 35, the photoreceptor AC-1, the photoreceptor AD-1, the photoreceptor CA-1, The above-described image quality evaluation 1 was performed on the photoconductor DA-1, the photoconductor CB-1, and the photoconductor DB-1. Furthermore, the evaluation shown in Table 11 among the image flow evaluations 1 to 10 was performed. The results are shown in Table 11.
From the above results, it can be said that an electrophotographic image forming apparatus satisfying the above requirements is an electrophotographic apparatus in which image flow hardly occurs and deterioration in image quality is suppressed.
(Examples 43 and 44)
The above-described image quality evaluation 3 was performed on the photoreceptors BA-1 and BB-1 having concave portions on the surface. Further, image flow evaluations 11 to 20 were performed. The results are shown in Table 12.
From the above results, it can be said that the electrophotographic image forming apparatus is an apparatus in which image flow hardly occurs and deterioration in image quality is suppressed even in the corona charging system.
(Examples 45-75)
The above-mentioned image quality evaluation 2 was performed on the photoreceptors AA-8, 9, 12-15, 18-20, and 22-24 having concave portions on the surface. Further, the photoreceptors AB-8, 9, 12-15, 18-20, 22-24, 31, 32, the photoreceptor AD-1, the photoreceptor CA-1, the photoreceptor DA-1, the photoreceptor CB-1, The above-mentioned image quality evaluation 2 was performed on the photoreceptor DB-1. Furthermore, the evaluation shown in Table 13 among the image flow evaluations 1 to 10 was performed. The results are shown in Table 13.
From the above results, it can be said that an electrophotographic image forming apparatus that satisfies the above requirements is an apparatus in which image flow hardly occurs and image quality deterioration is suppressed.
(Examples 76 and 77)
The above-mentioned image quality evaluation 4 was performed on the photoreceptors BA-1 and BB-1 having concave portions on the surface. Further, image flow evaluations 11 to 20 were performed. The results are shown in Table 14.
From the above results, it can be said that the electrophotographic image forming apparatus of this example is an apparatus in which image flow hardly occurs and deterioration in image quality is suppressed not only by the contact charging method but also by the corona charging method. .
(Comparative Examples 1-5)
The above-described image quality evaluation 1 was performed on the electrophotographic photoreceptors A to E having no concave portions on the surface. Further, image flow evaluations 2, 6, and 9 were performed. The results are shown in Table 15.
From the above results, it can be said that an electrophotographic apparatus using a photoconductor having no concave portion on the surface is an electrophotographic apparatus in which image flow is not sufficiently suppressed although image quality is not deteriorated.
(Comparative Examples 6 to 52)
The above-mentioned image quality evaluation 1 was performed on the photoreceptors AA-1 to 7, 16, 17, 21, 25 to 27, 30, 33, 34, and 36 to 40 having concave portions on the surface. Photoconductors AB-1 to 7, 10, 11, 16, 17, 21, 25 to 27, 30, 33, 34, 36 to 40, and photoconductor EA-1, photoconductor EB-1, and photoconductor P The above-described image quality evaluation 1 was performed. Furthermore, the evaluation shown in Table 16 among the image flow evaluations 1 to 10 was performed. The results are shown in Table 16.
From the above results, it can be said that an electrophotographic image forming apparatus that does not satisfy the above requirements is an apparatus that is insufficient in suppressing image flow and / or image quality degradation.
In particular, in Comparative Examples 50 and 51, the longest diameter, depth, area, and arrangement of the openings of the specific recesses of the photoreceptors EA-1 and EB-1 satisfy the same requirements as in the examples. However, since shape transfer by a mold is performed before the coating film is cured, the area of the flat portion is small and the effect of suppressing image flow is insufficient.
In Comparative Example 52, the area of the specific concave portion of the photoreceptor P is large and the area of the flat portion is small, so that the image flow is not sufficiently suppressed, and the arrangement of the concave portions does not satisfy the requirements of the example. The bitterness decreased.
(Comparative Examples 53 and 54)
The above-mentioned image quality evaluation 3 was performed on the photoreceptors BA-2 and 3 having concave portions on the surface. Further, image flow evaluations 13, 16, and 19 were performed. The results are shown in Table 17.
From the above results, it can be said that an electrophotographic image forming apparatus that does not satisfy the same requirements as in the embodiment is an apparatus that is insufficient in suppressing image flow and / or image quality degradation.
(Comparative Examples 55-112)
Photoconductors AA-1 to 11, 16, 17, 21, 25 to 40 having concave portions on the surface, photoconductors AB-1 to 11, 16, 17, 21, 25 to 30, 33 to 40, and photoconductor AC- 1. The above-described image quality evaluation 2 was performed on the photoconductor EA-1, the photoconductor EB-1, and the photoconductor P. Furthermore, the evaluation shown in Table 18 among the image flow evaluations 1 to 10 was performed. The results are shown in Table 18.
From the above results, it can be said that an electrophotographic image forming apparatus that does not satisfy the same requirements as in the embodiment is an apparatus that is insufficient in suppressing image flow and / or image quality degradation.
(Comparative Examples 113 and 114)
The above-described image quality evaluation 4 was performed on the photoreceptors BA-2 and 3 having concave portions on the surface. Further, image flow evaluations 13, 16, and 19 were performed. The results are shown in Table 19.
From the above results, it can be said that an electrophotographic image forming apparatus that does not satisfy the same requirements as in the embodiment is an apparatus that is insufficient in suppressing image flow and / or image quality degradation.
Thus, if the configuration of the embodiment is adopted, the prior art is further developed, and an electrophotographic apparatus and an electrophotographic photosensitive member in which image flow is less likely to occur and image quality deterioration due to a concave portion on the surface of the electrophotographic photosensitive member is further suppressed. The body can be provided.

  According to the present invention, there are provided an image forming apparatus and an electrophotographic photosensitive member that are less likely to cause image flow and that can suppress deterioration in image quality due to a concave portion on the surface of the electrophotographic photosensitive member.

  The present invention relates to an image forming apparatus and an electrophotographic photosensitive member.

  Since an electric external force such as charging or cleaning or a mechanical external force is applied to the surface of the electrophotographic photosensitive member, durability against such external force (such as wear resistance) is required.

  In response to this requirement, conventionally, improved techniques such as using a highly wear-resistant resin for the surface layer of the electrophotographic photosensitive member have been used.

  On the other hand, a problem caused by increasing the wear resistance of the surface of the electrophotographic photosensitive member is image flow. In the image flow, the material used for the surface layer of the electrophotographic photosensitive member deteriorates due to an oxidizing gas such as ozone or nitrogen oxide generated by charging of the surface of the electrophotographic photosensitive member, or electrophotography occurs due to moisture adsorption. This is considered to be caused by the fact that the surface of the photoreceptor is lowered in resistance. The higher the abrasion resistance of the surface of the electrophotographic photosensitive member, the more difficult the surface of the electrophotographic photosensitive member is refreshed (removal of materials that cause image flow such as deteriorated materials and adsorbed moisture), resulting in image flow. It becomes easy to do.

As a technique for improving image flow, Patent Document 1 discloses a technique for providing a dimple-shaped recess on the surface of an electrophotographic photosensitive member by dry blasting or wet honing. According to Patent Document 1 , by providing a plurality of dimple-shaped concave portions on the surface of the electrophotographic photosensitive member, it is possible to suppress image flow from the initial stage to about 5000 sheets.

Further, in Patent Document 2 , by providing a plurality of concave portions with a high area ratio on the surface of the electrophotographic photosensitive member, the dot reproducibility from the initial stage to about 50000 sheets can be maintained well even under a high temperature and high humidity environment. A technique for suppressing image flow is disclosed.

Patent Document 3 discloses a technique for providing a recess with a low area ratio on the surface of an electrophotographic photosensitive member.

  As described above, a technique for providing a plurality of recesses on the surface of an electrophotographic photosensitive member has been studied as a technique for suppressing image flow. In designing a plurality of recesses, items such as the surface roughness, the size of each recess, or the number of recesses in a certain area are attracting attention.

  On the other hand, there is an item “arrangement of recesses” as a design item for a plurality of recesses. Conventionally, the density of the recesses has been studied, but no attention has been paid to how the recesses are arranged.

As a technique paying attention to the arrangement of the recesses, Patent Document 2 discloses a technique for suppressing the growth of scratches by disposing the recesses within 50 μm in the rotation direction of the electrophotographic photosensitive member.

WO05 / 093518 (International Publication Number) JP 2007-233355 A JP 2011-22578 A

  The present invention is a further development of the above prior art. That is, an object of the present invention is to provide an image forming apparatus and an electrophotographic photosensitive member that are less likely to cause image flow and that can suppress deterioration in image quality due to a concave portion on the surface of the electrophotographic photosensitive member.

According to the present invention, an electrophotographic photosensitive member comprising at least a support and a photosensitive layer formed on the support;
An image forming apparatus comprising: an image forming unit that forms an electrostatic latent image on the electrophotographic photosensitive member using at least a screen pattern generated by a pseudo halftone process formed of dots as a method of expressing gradation Because
A plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less are formed on the surface of the electrophotographic photoreceptor,
When one side in the surface of the electrophotographic photoconductor were arbitrarily extracted square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the flat portion contained in the portion except the recess The total area is 80000 μm ² or more and 240000 μm ² or less,
The image forming apparatus, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.

<Calculation processing>
(1) from said screen pattern (B), remove the portions overlapping with the plurality of recesses, and the image (C) for (2) Image (C) subjected to particle analysis, the average value SM of dot area, dot Calculate the standard deviation (σ) of the area (3) Obtain the image quality degradation index (f) by the following equation (1). Equation (1): f = σ / SM
Is provided.

Further, according to the present invention, an electrophotographic photosensitive member comprising at least a support and a photosensitive layer formed on the support;
An image forming unit that forms an electrostatic latent image on the electrophotographic photosensitive member using at least a screen pattern generated by pseudo halftone processing formed of dots as a technique for expressing gradation, and the electrophotographic photosensitive member A blade that contacts and cleans the image forming apparatus,
A plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less are formed in at least a contact region with the blade on the surface of the electrophotographic photosensitive member,
When one side in the contact region is arbitrarily extract a square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the total area of the flat portion contained in the portion except the recess 80000μm ^{2 to} 240,000 μm ² ,
The image forming apparatus, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.

<Calculation processing>
(1) from said screen pattern (B), remove the portions overlapping with the plurality of recesses, and the image (C) for (2) Image (C) subjected to particle analysis, the average value SM of dot area, dot Calculate the standard deviation (σ) of the area (3) Obtain the image quality degradation index (f) by the following equation (1). Equation (1): f = σ / SM
Is provided.

Furthermore, according to the present invention, there is provided an electrophotographic photosensitive member on which an electrostatic latent image is formed using at least a screen pattern generated by a pseudo halftone process formed by dots as a technique for expressing gradation. ,
A support, and a photosensitive layer formed on the support,
On the surface of the electrophotographic photosensitive member, a plurality of recesses having a depth of 0.5 μm to 5 μm and a longest diameter of the opening of 20 μm to 80 μm are formed,
When one side in the surface of the electrophotographic photoconductor were arbitrarily extracted square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the flat portion contained in the portion except the recess The total area is 80000 μm ² or more and 240000 μm ² or less,
The electrophotographic photoreceptor, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.

<Calculation processing>
(1) from said screen pattern (B), remove the portions overlapping with the recess of the plurality of, and the image (C) for (2) Image (C) subjected to particle analysis, the average value SM of dot area, dot Calculate the standard deviation (σ) of the area (3) Obtain the image quality degradation index (f) by the following equation (1). Equation (1): f = σ / SM
Is provided.

Furthermore, according to the present invention, an electrostatic latent image is formed using at least a screen pattern generated by a pseudo halftone process formed of dots as a technique for expressing gradation, and the surface is cleaned by a blade. An electrophotographic photosensitive member,
A support, and a photosensitive layer formed on the support,
A plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less are formed in a contact area with the blade on the surface of the electrophotographic photoreceptor.
When one side in the contact region is arbitrarily extract a square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the total area of the flat portion contained in the portion except the recess 80000μm ^{2 to} 240,000 μm ² ,
The electrophotographic photoreceptor, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.

<Calculation processing>
(1) from said screen pattern (B), remove the portions overlapping with the recess of the plurality of, and the image (C) for (2) Image (C) subjected to particle analysis, the average value SM of dot area, dot Calculate the standard deviation (σ) of the area (3) Obtain the image quality degradation index (f) by the following equation (1). Equation (1): f = σ / SM
Is provided.

According to the present invention, it is possible to provide an image forming apparatus and an electrophotographic photosensitive member that are less likely to cause image flow and that can suppress deterioration in image quality due to a concave portion on the surface of the electrophotographic photosensitive member.

(A) And (B) is a figure which shows typically relations, such as a reference plane, a flat part, and a recessed part. (A)-(G) is a figure which shows the example of the shape of the opening part of the recessed part of the surface of an electrophotographic photoreceptor. (A)-(G) is a figure which shows the example of the cross-sectional shape of the recessed part of the surface of an electrophotographic photoreceptor. It is a figure which shows the example of the press-contact shape transfer processing apparatus for forming a recessed part in the surface of an electrophotographic photoreceptor. It is a figure which shows the example of an electrophotographic apparatus. (A)-(D) are figures which show the mold used by the manufacture example of the electrophotographic photoreceptor. It is a figure which shows the example of fitting. It is a figure which shows the result of having performed cross-sectional observation of the surface layer vicinity of an electrophotographic photoreceptor. It is a figure which shows the example of a dry-type blasting apparatus. It is a figure for demonstrating a narrow part. (A) is an enlarged view of an example of a screen used in pseudo halftone processing, and (b) shows an example of a recess arrangement in which recesses close to the dot size of the screen pattern having an aperture diameter (a) are irregularly arranged. (C) is a diagram showing an example of a recess arrangement in which recesses whose opening diameter is extremely smaller than the dot size of the screen pattern of (a) are irregularly arranged, and (d) is the recess arrangement of (b). The figure which assumed the output image at the time of outputting the screen image of (a) using the obtained electrophotographic photosensitive member, (e) is using the electrophotographic photosensitive member in which the concave portion arrangement of (c) is made. FIG. 5A is a diagram assuming an output image when a screen image is output, FIG. 5F is a diagram in which (d) is reduced and (g) is a diagram in which (e) is reduced. (A) is a square arrangement, and is an enlarged view of a screen having an angle of 45 ° when the main scanning direction of exposure light is 0 °, and (b) is a square arrangement when the main scanning direction of exposure light is 0 °. The figure which showed an example of the recessed part arrangement | positioning of angle 41.2 degrees, (c) is a figure which showed an example of recessed part arrangement | positioning of angle 26.6 degrees when (c) is square arrangement | positioning and the main scanning direction of exposure light is set to 0 degree, (D) is a view assuming an output image when the screen image of (a) is output using the electrophotographic photosensitive member having the concave portion arrangement of (b), and (e) is a drawing of the concave portion arrangement of (c). It is the figure which assumed the output image at the time of outputting the screen image of (a) using the electrophotographic photosensitive member which it was. It is a graph which shows an example of a VTF function (visual spatial frequency characteristic). (A) is a figure which shows the algorithm of the Floyd-Steinberg method, (b) is a figure which shows an example of the irregular pattern produced | generated by the Floyd-Steinberg method. (A) is a figure which shows an example of the mask used for the formation method of the recessed part by laser beam irradiation, (b) is a figure which shows an example of the recessed part formation apparatus by laser beam irradiation. It is a figure showing a dot concentration type dither matrix of 1200 dpi, 106 lpi, 45 degrees. It is a figure which shows an example of the photograph of the electrophotographic photoreceptor surface which has a recessed part acquired by GX-700.

  The feature of this example is that it combines the following four items.

Feature 1: The longest diameter (major axis diameter) of the opening of the recess is large. Feature 2: The proportion of the area of the recess is small. Feature 3: The proportion of the area of the flat portion is large. Feature 4: The recess satisfies the specific standard. The arranged features 1 to 3 are items for suppressing image flow, and a feature 4 is an item for suppressing deterioration in image quality. Details will be described below.

<Suppression of image flow>
First, features 1 to 3 that are items for suppressing image flow will be described. In the features 1 to 3 of this example, the feature of the technique described in the above-mentioned WO 05/093518 (International Publication Number) is that the ratio of the area of the flat portion on the surface of the electrophotographic photosensitive member is large. If using a dry blast treatment or a wet honing treatment is provided a recess dimple-shaped on the surface of the electrophotographic photosensitive member, to become the impinging particles randomly to the surface of the electrophotographic photosensitive member, a portion other than the recess ( The ratio of the area of the flat portion in the portion excluding the concave portion is extremely small.

  In addition, regarding the features described in Japanese Patent Application Laid-Open No. 2011-22578 in the features 1 to 3 of this example, the surface on the surface of the electrophotographic photosensitive member is flat as in the case of the features of WO05 / 093518 (International Publication Number). The ratio of the area of the part is large.

  In addition, in the features 1 to 3 of this example, the feature described in the above-mentioned Japanese Patent Application Laid-Open No. 2007-233355 and Japanese Patent Application Laid-Open No. 2007-233359 is that the concave portion having a large longest diameter (major axis diameter) is the The point provided on the surface of the photographic photosensitive member and the area ratio of the recesses are small.

  In this example, the area of the recess means that the surface of the electrophotographic photoreceptor is substantially parallel to the normal direction perpendicular to the surface of the photoreceptor (the radial direction in the case of a cylindrical photoreceptor) from above. It is the area of the recess when it is, and means the area of the opening of the recess. The same applies to flat portions and convex portions.

  The results of the study by the present inventors were as follows. A recess having a large longest diameter of the opening (preferably a recess having a large shortest diameter of the opening) is sparsely arranged on the surface of the electrophotographic photosensitive member, and the area of the flat portion is particularly large among the portions other than the recess. Take. As a result, it has been found that the effect of suppressing image flow is dramatically improved. That is, a sufficient effect can be obtained for an image flow that occurs remarkably in the vicinity of the charging device, or an image flow immediately after startup that is likely to occur when the electrophotographic apparatus is left for several days in a high-temperature and high-humidity environment. all right.

  By sparsely arranging the recesses with the longest diameter of the opening, chattering of the cleaning blade is moderately suppressed, and a stable rubbing state between the surface of the electrophotographic photosensitive member and the cleaning blade is created. At the same time, the pressure of the cleaning blade with respect to the recesses is relatively low, so that the pressure with respect to portions other than the recesses is relatively high. In addition to the concave portions where the pressure increases, the image flow causative substance adhering to the surface of the electrophotographic photosensitive member is increased by increasing the number of flat portions on which the surface of the electrophotographic photosensitive member can be efficiently refreshed. It becomes easy to be removed.

  The present inventors believe that the image flow suppression effect is dramatically improved by such a mechanism.

  Specifically, the surface of the electrophotographic photoreceptor is provided with a plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less. A plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less are also referred to as “specific recesses”.

The specific recess is provided on the surface of the electrophotographic photosensitive member as follows when a square region (area: 250,000 μm ² ) having a side of 500 μm is arranged (extracted) at an arbitrary position on the surface of the electrophotographic photosensitive member. That is, the area of the particular recess one side is in the 500μm square area of (the total area) is provided so that the 10000 ² more 90000Myuemu ² or less.

  In addition, when the surface of the electrophotographic photosensitive member is a curved surface, it is as follows. For example, when the electrophotographic photosensitive member is cylindrical, the surface (circumferential surface) of the electrophotographic photosensitive member is a curved surface curved in the circumferential direction. In this case, “arranging a square region having a side of 500 μm at an arbitrary position on the surface of the electrophotographic photosensitive member” means that when the curved surface is corrected to a flat surface, the region that becomes a square in the flat surface is the electrophotographic photosensitive member. It means that it is arranged at an arbitrary position on the surface of.

In addition to the specific recess, a flat portion is provided on the surface of the electrophotographic photosensitive member. The flat portion is provided on the surface of the electrophotographic photosensitive member as follows. That is, when a square region having a side of 500 μm is arranged at an arbitrary position on the surface of the electrophotographic photosensitive member, the area (total area) of the flat portion in the square region having a side of 500 μm is set to be 80000 μm ² or more and 240000 μm ² or less. It is done.

  The specific concave portion or flat portion on the surface of the electrophotographic photosensitive member can be observed using a microscope such as a laser microscope, an optical microscope, an electron microscope, or an atomic force microscope.

  As the laser microscope, for example, the following devices can be used. Keyence Corporation ultra-deep shape measurement microscope VK-8550, ultra-deep shape measurement microscope VK-9000, ultra-deep shape measurement microscope VK-9500, VK-X200. Surface shape measuring system Surface Explorer SX-520DR type machine manufactured by Ryoka System Co., Ltd. Scanning confocal laser microscope OLS3000 manufactured by Olympus Corporation. Real color confocal microscope Oplitex C130 manufactured by Lasertec Corporation.

  As the optical microscope, for example, the following devices can be used. Keyence Corporation digital microscope VHX-500, digital microscope VHX-200. 3D digital microscope VC-7700 manufactured by OMRON Corporation.

  As the electron microscope, for example, the following devices can be used. Keyence 3D Real Surface View Microscope VE-9800, 3D Real Surface View Microscope VE-8800. Scanning electron microscope conventional / variable pressure SEM manufactured by SII Nanotechnology. A scanning electron microscope SUPERSCAN SS-550 manufactured by Shimadzu Corporation.

  As the atomic force microscope, for example, the following devices can be used. Nanoscale hybrid microscope VN-8000 manufactured by Keyence Corporation. Scanning probe microscope NanoNavi station manufactured by SII Nanotechnology. Scanning probe microscope SPM-9600 manufactured by Shimadzu Corporation.

  The observation of the 500 μm square area and the observation for obtaining the image (C) described below may be performed at a low magnification or after a partial observation at a high magnification as long as the specific concave portion can be identified. A plurality of partial images may be connected using software or the like.

  The determination (definition) of the specific recessed portion and the flat portion in a square region having a side of 500 μm will be described.

  First, the surface of the electrophotographic photoreceptor is enlarged and observed with a microscope. For example, when the surface (circumferential surface) of the electrophotographic photosensitive member is a curved surface curved in the circumferential direction as in the case where the electrophotographic photosensitive member is cylindrical, a cross-sectional profile of the curved surface is extracted and a curved line ( If the electrophotographic photosensitive member is cylindrical, an arc) is fitted.

  FIG. 7 shows an example of fitting. The example shown in FIG. 7 is an example when the electrophotographic photosensitive member is cylindrical. In FIG. 7, a solid line 701 is a cross-sectional profile of the surface (curved surface) of the electrophotographic photosensitive member, and a broken line 702 is a curve fitted to the cross-sectional profile 701. The cross-sectional profile 701 is corrected so that the curve 702 becomes a straight line, and a surface obtained by extending the obtained straight line in the longitudinal direction (direction perpendicular to the circumferential direction) of the electrophotographic photosensitive member is used as a reference surface. Even when the electrophotographic photosensitive member is not cylindrical, the reference surface is obtained in the same manner as when the electrophotographic photosensitive member is cylindrical.

  The surface that is located 0.2 μm below the obtained reference surface and is parallel to the reference surface is the second reference surface, the surface that is 0.2 μm above the reference surface and is parallel to the reference surface is the third reference surface. To do. Of the square region having a side of 500 μm, a portion sandwiched between the second reference surface and the third reference surface is defined as a flat portion in the square region. A portion located above the third reference plane is defined as a convex portion in the square area. A portion located below the second reference plane is defined as a recess in the square area.

  The distance from the second reference plane to the lowest point of the recess is defined as the depth of the recess. Let the cross section of the recessed part by a 2nd reference surface be an opening part of a recessed part, and let the length of the longest line segment be the longest diameter of the opening part of a recessed part among the line segments which cross an opening part.

  The depth determined in this manner is in the range of 0.5 μm or more and 5 μm or less, and the longest diameter of the opening is in the range of 20 μm or more and 80 μm or less corresponds to the specific recess among the recesses. The depth of the specific recess in this example is preferably in the range of 1 μm to 5 μm. Further, the distance when the distance between the two parallel lines sandwiching the opening of the recess is the shortest is the shortest diameter of the opening of the recess. The shortest diameter of the opening of the specific recess in this example is preferably in the range of 20 μm to 80 μm.

  1A and 1B, the relationship between the reference surface 101, the flat portion (the portion sandwiched between the second reference surface 102 and the third reference surface 103), the concave portion 104 (specific concave portion), the convex portion 105, and the like. This is shown schematically. 1A and 1B are cross-sectional profiles after the above correction.

  2A to 2G show examples of the shape of the opening of the specific recess (the shape when the specific recess is viewed from above). Moreover, the example of the cross-sectional shape of a specific recessed part is shown to FIG. 3 (A)-(G).

  Examples of the shape of the opening of the specific recess include a circle, an ellipse, a square, a rectangle, a triangle, a quadrangle, and a hexagon as shown in FIGS. Moreover, as a cross-sectional shape of a specific recessed part, as shown to FIG. 3 (A)-(G), what has edges, such as a triangle, a square, a polygon, the waveform which consists of a continuous curve, and a triangle , Quadrilaterals, polygonal edges partially or entirely deformed into curves, and the like.

  The plurality of specific recesses provided on the surface of the electrophotographic photoreceptor may all have the same shape, the longest diameter and depth of the opening, or may have different shapes, the longest diameter and depth of the opening. It may be mixed.

  The specific recess may be formed on the entire surface of the electrophotographic photosensitive member, or may be formed on a part of the surface of the electrophotographic photosensitive member. When the specific recess is formed on a part of the surface of the electrophotographic photosensitive member, it is preferable that the specific recess is formed at least in the entire contact area with the cleaning member.

  In addition, the flat portion provided on the surface of the electrophotographic photosensitive member preferably has a certain size from the viewpoint of enhancing the removability of the substance causing the image flow, and there are few narrow flat portions (narrow portions). Is preferred. Specifically, the ratio of the area of the narrow portion where the 10 μm side square area cannot be arranged among the flat parts in the 500 μm side square area arranged at an arbitrary position on the surface of the electrophotographic photosensitive member is as follows. It is preferable that it seems. That is, it is preferably 30% or less with respect to the entire area of the flat portion in the square region having a side of 500 μm. However, even if the area of the narrow portion is 30% or more, the effect in this example can be obtained.

  FIG. 10 is a diagram for explaining a narrow portion. FIG. 10 shows an example of a shape when a part of the surface of the electrophotographic photosensitive member is viewed from above. In FIG. 10, for ease of explanation, a case where all the portions that are not specific recesses are flat portions is taken as an example.

  In FIG. 10, reference numeral 1001 denotes a specific concave portion on the surface of the electrophotographic photosensitive member, 1002 denotes a square region having a side of 10 μm arranged on the flat portion of the surface of the electrophotographic photosensitive member, and 1003 denotes a narrow portion (black in the drawing). The part that is filled). The square region 1002 may be arranged in any direction on the flat portion as indicated by a broken-line square in the drawing. A portion where the square region 1002 cannot be arranged in any direction in the flat portion becomes a narrow portion 1003 in the flat portion.

<Suppression of image quality degradation>
Next, feature 4 which is an item for suppressing image quality deterioration will be described. As a result of investigations by the present inventors, the image quality may be deteriorated by providing a plurality of recesses on the surface of the electrophotographic photosensitive member. The reason for this is that the concave portions tend to have inferior electrophotographic characteristics as compared with portions that are not concave portions. The electrophotographic characteristics are charging ability, latent image reproducibility, development efficiency or transfer efficiency. If the electrophotographic characteristics of the recess are inferior, the portion of the image data that is imaged in the recess of the electrophotographic photosensitive member cannot be faithfully reproduced. As a result, the output image is shaded according to the arrangement of the recesses, and the granularity (roughness) of the image is reduced.

  Furthermore, when pseudo halftone processing formed with dots is used as a method of expressing gradations, moire is generated in addition to a decrease in graininess. The decrease in graininess (guzziness) and moire are caused by the following mechanism.

  First, the halftone is converted into image data composed of a set of small dots called a screen by pseudo halftone processing. When the screen is imaged, the portion overlapping the concave portion is not faithfully reproduced, so that dots are lost. Since the degree of missing dots depends on the degree of overlap between the recesses and the dots, the missing dots are not uniform and vary. At this time, if the variation in dot missing is large, the graininess is lowered. Furthermore, depending on the relationship between the screen pattern and the arrangement of the recesses, the dot missing variation appears periodically. As a result, periodic shading, that is, moire occurs in the output image.

  As a result of the study by the present inventors, when using pseudo halftone processing formed with dots as a method of expressing gradation, it is possible to suppress image quality degradation by arranging the concave portions so as to satisfy a specific standard. I understood. The deterioration in image quality is graininess (guzziness) and moire. An outline of these will be described.

  First, a description will be given of a decrease in graininess (guzziness). Generally, an electrophotographic apparatus uses pseudo halftone processing as a technique for expressing gradation. The pseudo halftone processing is a method of expressing the gray scale by using only two colors of white and black to control the number of pixels and how the pixels are gathered. Of course, it can also be used for color.

  There are various pseudo-halftone processing patterns (screens) such as parallel lines, wavy lines, and grain, but the method of representing them by a set of small dots is the mainstream. For pseudo halftone processing formed with dots, AM dot screening with regular dot placement and changing the dot size and density to express shading, irregular dot placement with fixed dot diameter, There is FM screening that expresses shading by changing the density. Although the following description will be given for AM screening, the pseudo halftone processing in this example may be either AM screening or FM screening.

  FIG. 11A is an example of an enlarged screen by AM screening. On the other hand, the surface of the electrophotographic photoreceptor can be designed in various ways with respect to the size and arrangement of the recesses. FIGS. 11B and 11C show examples in which the opening of the recess is expressed in black and the portion other than the recess is expressed in white. (B) is an irregular arrangement of depressions with square openings and recess opening sizes close to the dot size. (C) is an irregular arrangement of depressions with square openings and small opening sizes with respect to the dot size. (B), (c) is an example for explanation, and is not limited to this.

  The concave portion tends to deteriorate the electrophotographic characteristics, and in some cases, the concave portion is not image-formed. That is, when the above-described screen dots are formed on the recesses, the dots are missing. When the screen image of (a) is output using the electrophotographic photosensitive member in which the concave portions of (b) and (c) are arranged, the output images are assumed to be (d) and (e). Each dot is missing depending on the degree of overlap with the recess, and it can be seen that the variation in dot missing is larger in (d) than in (e).

  Although the screen is enlarged here, the pseudo halftone process actually uses an optical illusion and is used with a dot size that cannot be recognized by the human eye. (F) and (g) show images obtained by reducing (d) and (e) to some extent. It can be seen that the variation in dot missing (f) is larger, the variation in shading is larger, and the graininess (grid) is reduced.

  Next, moire will be described. In the example of the above-described decrease in graininess (gutteriness), the graininess (gutteriness) is reduced by a combination of a regular screen and an irregular recess arrangement. On the other hand, in the case of a combination of a regular screen and a regular recess arrangement, interference occurs between patterns, and dot missing variation (shading) appears periodically, so-called moire (interference fringes) occurs.

  As an example of a regular screen, FIG. 12A shows a screen having a square arrangement and a square arrangement angle of 45 ° when the exposure light main scanning direction (horizontal direction in this figure) is 0 °. Show. As an example of the regular recess arrangement, (b) and (c) are shown in which the shape of the opening is circular and the arrangement is a square arrangement. (B) is a square arrangement angle of 41.2 °, and (c) is 26.6 °. When the screen image of (a) is output using the electrophotographic photosensitive member in which the concave portions of (b) and (c) are arranged, the output images are (d) and (e). When viewed microscopically, interference occurs in both (d) and (e), and the variation of dot missing appears periodically.

  However, when (d) and (e) are viewed macroscopically, (d) is more prominent in periodic shading. This is because the longer the shade period, the higher the visual resolution. On the other hand, if the period of light and shade becomes very short as shown in (e), it will not be visually recognized as moiré by human eyes.

  Further, the interference has a characteristic that the longer the period, that is, the lower the wave number, is when the concave portion is closer to the number of lines and the angle of the screen. In the recess arrangement of (b) and (c), the angle 41.2 ° of (b) is closer to the screen angle 45 ° of (a) than the angle 26.6 ° of (c).

  As a result, the period of interference is longer in (d) than in (e), that is, it has a low wavenumber, and is therefore easily visible. Therefore, the problem of image quality is low wave number moire.

  As described above, the technique of providing a plurality of concave portions on the surface of the electrophotographic photosensitive member has problems of image quality deterioration, that is, graininess reduction and moire.

<Image quality degradation index>
The calculation processes (1) to (3), which are methods for calculating the image quality degradation index (f), will be described in detail.

(1) From the screen pattern (B) generated by the pseudo halftone process formed by dots, a portion overlapping with the plurality of concave portions is deleted to obtain an image (C) .
This process is a process of creating a pseudo output image by image processing. The screen pattern (B) generated by the pseudo halftone process formed by dots is, for example, (a) in FIG. 11 and (a) in FIG. Images (C) obtained by deleting portions overlapping the plurality of recesses from the screen are, for example, (d) and (e) in FIG. 11 and (d) and (e) in FIG.

  As described above, the concave portion tends to have inferior electrophotographic characteristics as compared with the non-concave portion, and the image is missing. The electrophotographic characteristics are charging ability, latent image reproducibility, development efficiency or transfer efficiency. Since the concave portion has a smaller thickness of the photosensitive layer than the non-recessed portion and has a large capacitance, or the contact with the charging member becomes insufficient, the charging ability may be lowered. In addition, the concave portion may have a lower photosensitive film thickness than the non-recessed portion, and the sensitivity may be reduced, or exposure light may be refracted due to the shape of the concave portion, thereby reducing the latent image reproducibility.

  In addition, since the concave portion is insufficiently brought into contact with the transfer member and the toner carried on the developing member, the transfer efficiency and the developing efficiency may be lowered. The electrophotographic characteristics of the recesses do not necessarily deteriorate because they depend on the photosensitive layer, the size of the recesses, the toner, the electrophotographic process, or the surrounding environment.

  However, an object in this example is to provide an electrophotographic apparatus in which image quality degradation due to the concave portion is suppressed under any conditions. Therefore, in calculating the image quality degradation index (f), image data Of these, the portion formed in the recess is treated as not printed.

  The screen pattern (B) is generated by a pseudo halftone processing algorithm set in the electrophotographic apparatus when a gray scale is output by the electrophotographic apparatus. Therefore, the screen pattern (B) can be obtained from the gray scale density and the pseudo halftone processing algorithm. Alternatively, the screen pattern (B) can be obtained by setting the density, resolution, dot shape, and number of lines using Adobe Photoshop (registered trademark) or the like.

  Note that in the case of an electrophotographic apparatus using multi-value pseudo halftone processing using PWM (pulse width modulation) or the like, binarization is performed with a half-value (50%) threshold value of multi-value information, and a screen pattern ( B).

  The screen pattern (B) can also be obtained by observing a toner image formed on the photoreceptor. Specifically, image output is performed using a photoconductor that does not have a concave shape on the surface, and the electrophotographic apparatus is turned off during output to stop the image with a toner image on the photoconductor. As a result, a toner image without image quality deterioration is obtained on the photoreceptor. A micrograph of the screen pattern (B) can be obtained by observing the toner image on the photoreceptor with a microscope such as the above-mentioned laser microscope or optical microscope.

  Subsequently, image processing is performed on the obtained micrograph to generate binarized image data. Any method may be used for generating the binarized image data. For example, the obtained micrograph is obtained by performing the following binarization process.

If the photoconductor is a cylindrical body, the curvature component is corrected (similar to the fitting shown in FIG. 7 above).
-Remove noise components while leaving edges with median filter-Binarize with 50% threshold of difference between minimum luminance (toner image) and maximum luminance (photoconductor)-Remove minute area (remove fine particles such as minute toner)
・ Fill the area surrounded by the toner image (fill hole)
Such an image processing calculation can be performed using particle analysis software (GRADING ANALYSIS) manufactured by Keyence Corporation.

  The arrangement (A) of the plurality of recesses on the photoreceptor is also obtained by observation and binarization processing using a microscope such as the above-mentioned laser microscope, optical microscope, electron microscope, and atomic force microscope. The binarization process can be performed by the same method as the image process used in the screen pattern (B). However, since the specific recess is a portion below the second reference plane, it is necessary to reflect the opening shape of the specific recess determined by a microscope capable of obtaining three-dimensional information. Alternatively, by using analysis software attached to a microscope capable of obtaining three-dimensional information, the obtained micrograph can be binarized directly above and below the second reference plane.

  In addition, when the method of forming the recesses on the surface of the photoreceptor is a method of pressing a mold having projections, which will be described later, against the surface of the electrophotographic photoreceptor, the outer peripheral shape of the projections of the mold and the recesses on the surface of the photoreceptor The recesses can be formed so that the opening shapes are the same. Therefore, it is good also as arrangement | positioning of a recessed part with the electronic data at the time of mold observation or a mold design.

  Also, when the method of forming the recess is laser light irradiation described later, the recess can be formed so that the opening shape of the recess is the same as the opening shape of the mask. Therefore, it is good also as arrangement | positioning of a recessed part with the electronic data at the time of observation of a laser mask, or designing a mask.

  The shape of the image (C), that is, the arrangement of the plurality of recesses on the photoconductor (A) and the acquired shape of the screen pattern (B) contribute as much as possible in order to correctly evaluate the moire generated in a specific direction. Are equally preferred, and squares and circles are preferred.

  The area of the image (C), that is, the acquired areas of (A) and (B) is 400 dots or more of the screen pattern (B) from the viewpoint of the reliability of the standard deviation (σ) of the dot area described later. Area is preferred. In order to correctly evaluate the image quality, an appropriate area is selected from human visual characteristics. For example, it can be determined from a VTF function (visual spatial frequency characteristic) representing visual resolving power with respect to wave number (line number) shown in FIG. FIG. 13 is a VTF function with an observation distance of 300 mm, in which the vertical axis represents visual sensitivity and the horizontal axis represents wave number (number of lines).

  In FIG. 13, the visual sensitivity (vertical axis) when the wave number (horizontal axis) is about 1 (lpi) is sufficiently low, that is, even if the density change occurs at a cycle longer than 1 (lpi), It is invisible to the eyes. Therefore, the acquisition area can be a square region having one side of 25.4 mm.

  Alternatively, a square region having a side of 21.2 mm can be formed in accordance with the image quality attribute and the measurement method shown in ISO 13660. Alternatively, the standard deviation (σ) of the dot area, which will be described later, can be greater than or equal to the area that does not depend on the acquisition area. For example, if the patterns (A) and (B) are homogeneous, the standard deviation (σ) of the dot area does not depend on the acquired area even if the acquired area is small. Therefore, the acquisition area can be appropriately set according to the patterns (A) and (B).

  In the embodiment, the area where (σ) does not depend on the acquired area is verified. The acquisition range of the plurality of recesses (A) and the screen pattern (B) on the photoconductor was a 10.84 mm square area (corresponding to 1024 dots at 10.84 mm = 2400 dpi). However, it goes without saying that the ranges of (A) and (B) in this example may be set appropriately from the above viewpoint, and may not be a square region of 10.84 mm.

  When the arrangement range (A) of the plurality of recesses on the photoconductor and the acquisition range of the screen pattern (B) are wide, the image connection function of the above-described microscope group is effective. Or you may acquire using the GX-700 by Rebox Co., Ltd. which can image | photograph a wide area with a CCD camera. FIG. 17 shows a photograph of the surface of the electrophotographic photosensitive member having recesses, acquired by GX-700. This CCD photograph can be binarized to form a plurality of concave portions (A) and a screen pattern (B). In the case of the arrangement (A) of a plurality of recesses, it is preferable that the shape of the specific recess is grasped by the above-described microscope group and reflected in the binarized image.

  Further, when the screen pattern (B) generated by the pseudo halftone process formed by dots is acquired by microscopic observation, the following can be performed if AM screening is performed. That is, based on the result of partial microscopic observation, commercially available software can be used to generate binarized image data having a large area. After obtaining a micrograph of a part and binarization processing, the resolution can be determined from the dot diameter. Furthermore, in the main scanning direction and the sub-scanning direction of image exposure, the distance between the adjacent shortest dots can be measured, and the angle and the number of lines can be determined by calculation. As an example, Table 1 shows a case of a square arrangement with a resolution of 2400 dpi.

  For example, when the adjacent shortest dot interval measured from the binarized image is 2 dots for main scanning and 9 dots for sub scanning, it can be said that the dot period is 3 periods for main scanning and 10 periods for sub scanning. When the intersection of 3 main scanning cycles and 10 sub-scanning cycles is seen in Table 1, it can be seen that the screen angle is 73.3 ° and the number of lines is 230 (lpi). If the resolution, angle, and number of lines can be grasped in this way, binarized image data of a large area is generated using a conversion method from Adobe Photoshop's gray scale to monochrome two-tone (halftone screen). can do.

  The same method can be used for the arrangement (A) of the plurality of recesses on the photoreceptor when they are arranged as in the AM screening. The image quality degradation index (f) may be calculated using the binarized image data generated as described above.

  In any of the above-described means, when grasping the arrangement (A) of the plurality of concave portions of the photosensitive member, the opening shape of the specific concave portion is determined according to the criteria described in FIG.

(2) Particle analysis is performed on the image (C), and an average value SM of dot areas and a standard deviation (σ) of dot areas are calculated.

Particle analysis is performed on the image (C) that is a binary image, and the individual areas of all the dots in the image (C) are grasped. The particle analysis can be performed using commercially available software such as Keyence Corporation particle analysis software (GRADING ANALYSIS). Based on this data, an average value SM of dot areas and a standard deviation (σ) of dot areas are calculated. The average value SM of the dot areas is an arithmetic average (value) obtained by dividing the total sum of the dot areas S _i by the number n of all dots, and is obtained by Expression (2).

The standard deviation (σ) of the dot area is the square root of the variance (σ ² ) derived from the following equation (3), where S _i is the area of a certain dot and n is the number of all dots, and the variation in dot area A value representing the degree. The standard deviation (σ) of the dot area means that the smaller the value, the smaller the dot area variation, and the lower the image quality, that is, the graininess (cracking) and the moire are suppressed.

(3) The image quality degradation index (f) is obtained by the following equation (1). F = σ / SM Equation (1)
Since the standard deviation (σ) of the dot area depends on the average value SM of the dot areas, the image quality degradation of the screen pattern (B) having a large dot diameter and the screen pattern (B) having a small dot diameter are simply compared. I can't. Therefore, for standardization, the standard deviation (σ) of the dot area is divided by the average value SM of the dot areas.

  As a result of investigations by the present inventors, it is possible to suppress the deterioration of the image quality by arranging the recesses so that the image quality degradation index (f) obtained by quantifying the degree of decrease in the variation of the dot defect described above becomes 14% or less. I understood. When the image quality degradation index (f) is 14% or less, it means that variation in dot missing is small, and graininess degradation and moire are suppressed.

<Arrangement of recesses on the surface of the electrophotographic photoreceptor>
The recess arrangement in which the image quality degradation index (f) is 14% or less is not limited as long as the features 1 to 3 that are items for suppressing image flow are satisfied. Separately, there is a method of suppressing image quality deterioration by using FM halftone processing instead of the concave portion arrangement, but FM screening itself tends to reduce the roughness. Therefore, in electrophotographic apparatuses, AM screening and FM screening are generally used according to the required image quality.

  In order to perform the concave arrangement for reducing the image quality degradation index for AM screening, for example, a method of mixing a plurality of types of opening diameters of the concave parts can be mentioned. Further, there is a method in which the opening diameter of the recesses or the density of the recesses is much larger or smaller than the dot diameter of the screen pattern (B). However, the opening diameter of the recesses and the density of the recesses have an appropriate range for image flow suppression, which is another effect, and the AM screening pattern is designed because the dot diameter and density change depending on the density and resolution. Tend to be narrower. The following two methods are effective for designing the recess arrangement.

  One is a method of optimizing the direction of the arrangement of the concave portions with respect to the AM screening pattern by the pseudo halftone process formed by regularly arranging the concave portions and the dots to be output. In the case where the concave portions are regularly arranged, the granularity (roughness) is not easily lowered, but low wave number moire is likely to occur. Low wave number moire is likely to occur when the concave portion arrangement is close to the number of lines and angle of the pattern of the pseudo halftone processing, so the arrangement angle of the concave portion arrangement and the screen pattern angle should be arranged as close to orthogonal as possible. Thus, the image quality degradation index (f) can be lowered.

  The other is a method of irregularly arranging the recesses. When the concave portions are regularly arranged, for example, in a tandem machine, the angle of the AM screening pattern is different for each color. Therefore, it is necessary to design the concave portion according to each color, and the design freedom is narrowed. On the other hand, if the concave portions are irregularly arranged, the image quality degradation index (f) can be lowered at any AM screening pattern angle. However, since the granularity (roughness) tends to be lower than when the recesses are regularly arranged, it is preferable to design the recesses together with the opening diameter and density.

  As a means for irregularly arranging the concave portions on the surface of the photoreceptor, any method may be used as long as the image quality degradation index (f) can be lowered. In particular, when the method of forming the recesses on the surface of the photoconductor is a method that can intentionally control the arrangement of the recesses, an FM screening technique, which is one of pseudo halftone processing, can be applied to the design. it can. The method of intentionally controlling the arrangement of the concave portions includes a method of pressing a mold having a convex portion, which will be described later, against the surface of the electrophotographic photosensitive member, and a method of forming the concave portions by laser light irradiation.

  FM screening is a pseudo halftone process in which the dot diameter is fixed, irregular dot arrangement is performed, and gradation is expressed by changing the dot density. The offset printing machine, the electrophotographic printer, and the inkjet method are used. It is used in many image forming apparatuses. An irregular recess arrangement can be designed using a randomizing algorithm that generates an irregular dot arrangement for FM screening. Various randomization algorithms have been developed, and any method may be used as long as the image quality degradation index (f) becomes low.

  In the embodiment, the Floyd-Steinberg method is used among error diffusion which is the most general FM screening. The Floyd-Steinberg method distributes a difference (error) between a signal value of a target pixel of image data and a signal value when the target pixel is binarized to neighboring pixels.

  An example is shown in FIG. In this figure, 7/16 of the error of the pixel of interest is added to the signal value of the pixel right next to the pixel of interest. The error of the pixel of interest is distributed to the lower right, lower, and lower left pixels at the rate shown in the figure. The other pixels reflect this distribution result and binarize sequentially. As a result, a pattern having a non-periodic characteristic as shown in (b) can be generated. At this time, it is possible to design an arbitrary recess opening size, recess density, and recess arrangement by changing the pixel size, the distribution ratio, and the number of pixels to be distributed.

<Method for forming recesses on the surface of an electrophotographic photoreceptor>
The method for forming the recess is not particularly limited as long as the method can satisfy the requirements for the recess. For example, a method for forming the surface of an electrophotographic photosensitive member by irradiation with laser light having an output characteristic with a pulse width of 100 ns (nanoseconds) or less, and a shape transfer by pressing a mold having a predetermined shape against the surface of the electrophotographic photosensitive member The method of performing is mentioned.

  A method of forming a recess by laser light irradiation having an output characteristic with a pulse width of 100 ns (nanoseconds) or less will be described.

  Specific examples of the laser used in this method include an excimer laser using a gas such as ArF, KrF, XeF or XeCl as a laser medium or a femtosecond laser using titanium sapphire as a medium. Furthermore, the wavelength of the laser beam in the laser irradiation is preferably 1,000 nm or less.

  The excimer laser is laser light emitted in the following steps. First, high energy such as discharge, electron beam or X-ray is applied to a mixed gas of a rare gas such as Ar, Kr or Xe and a halogen gas such as F or Cl to excite the above elements. And combine them. Thereafter, excimer laser light is emitted when dissociating by falling to the ground state. Examples of the gas used in the excimer laser include ArF, KrF, XeCl, and XeF, and any of them may be used. In particular, KrF or ArF is preferable.

As a method for forming the concave portion, a mask in which a laser light blocking portion 2601 and a laser light transmitting portion 2602 are appropriately arranged as shown in FIG. Only laser light that has passed through the mask is condensed by the lens and irradiated onto the workpiece, so that a recess having a desired shape and arrangement can be formed. Since a large number of recesses within a certain area can be processed simultaneously instantly regardless of their shape and area, the process can be performed in a short time. Laser irradiation using a mask processes several mm ² to several cm ² per irradiation.

  In laser processing, as shown in FIG. 15B, first, the electrophotographic photosensitive member 2704 as a work is rotated by a work rotating motor 2702. While rotating, the workpiece moving device 2703 shifts the laser irradiation position of the laser oscillation unit 2701 in the axial direction of the electrophotographic photosensitive member 2704, thereby efficiently forming concave portions over the entire surface of the electrophotographic photosensitive member 2704. Can do. The depth of the concave portion can be adjusted within a desired range depending on the irradiation time and the number of irradiation times of the laser beam. According to such a configuration, it is possible to realize rough surface machining with high controllability of the size, shape, and arrangement of the recesses, and with high accuracy and high flexibility.

  Next, a method for forming a recess for transferring a shape by pressing a mold having a protrusion corresponding to the recess to be formed to the surface of the electrophotographic photosensitive member will be described. FIG. 4 shows an example of a press-contact shape transfer processing apparatus for forming concave portions on the surface of the electrophotographic photosensitive member.

  According to the press-fitting shape transfer processing apparatus shown in FIG. 4, while rotating the electrophotographic photosensitive member 401 as a workpiece, the mold 402 is continuously brought into contact with the surface (circumferential surface) and pressurized, thereby allowing the electron to move. A concave portion or a flat portion can be formed on the surface of the photoconductor 401.

  Examples of the material of the pressure member 403 include metal, metal oxide, plastic, and glass. Among these, stainless steel (SUS) is preferable from the viewpoint of mechanical strength, dimensional accuracy, and durability. The pressure member 403 is provided with a mold on the upper surface thereof. Further, the mold 402 can be brought into contact with the surface of the electrophotographic photosensitive member 401 supported by the support member 404 with a predetermined pressure by a support member (not shown) on the lower surface side and a pressure system (not shown). Further, the support member 404 may be pressed against the pressure member 403 with a predetermined pressure, or the support member 404 and the pressure member 403 may be pressed against each other.

  The example shown in FIG. 4 is an example in which the surface of the electrophotographic photosensitive member 401 is continuously processed while being driven or driven and rotated by moving the pressing member 403. Further, the surface of the electrophotographic photosensitive member 401 is continuously processed by fixing the pressure member 403 and moving the support member 404 or by moving both the support member 404 and the pressure member 403. You can also. Note that it is preferable to heat the mold 402 and the electrophotographic photosensitive member 401 from the viewpoint of efficiently performing shape transfer.

  Examples of the mold include a fine surface-treated metal and resin film, and a silicon wafer surface patterned with a resist. Moreover, what gave the metal coating to the resin film in which microparticles | fine-particles were disperse | distributed and the resin film which has a fine surface shape is mentioned. Moreover, it is preferable to install an elastic body between the mold and the pressure member from the viewpoint of making the pressure pressed against the electrophotographic photosensitive member uniform.

<Configuration of electrophotographic photoreceptor>
The electrophotographic photoreceptor of this example has a support and a photosensitive layer formed on the support. Examples of the shape of the electrophotographic photosensitive member include a cylindrical shape, a belt (endless belt) shape, and a sheet shape.

  The photosensitive layer may be a single-layer type photosensitive layer containing a charge transport material and a charge generation material in the same layer, or a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. It may be a laminated type (functionally separated type) photosensitive layer separated. From the viewpoint of electrophotographic characteristics, a laminated photosensitive layer is preferred. Further, the laminated photosensitive layer may be a normal photosensitive layer in which the charge generation layer and the charge transport layer are laminated in this order from the support side, or a reverse layer in which the charge transport layer and the charge generation layer are laminated in this order from the support side. Type photosensitive layer. From the viewpoint of electrophotographic characteristics, a normal layer type photosensitive layer is preferred. In addition, the charge generation layer may have a stacked structure, and the charge transport layer may have a stacked structure.

  The support is preferably one that exhibits conductivity (conductive support). Examples of the material of the support include metals (alloys) such as iron, copper, gold, silver, aluminum, zinc, titanium, lead, nickel, tin, antimony, indium, chromium, aluminum alloy, and stainless steel. In addition, for example, a metal support or a plastic support having a film formed by vacuum deposition using aluminum, an aluminum alloy, or an indium oxide-tin oxide alloy can be used.

  In addition, a support obtained by impregnating plastic or paper with conductive particles such as carbon black, tin oxide particles, titanium oxide particles, and silver particles, or a support made of conductive binder resin can also be used.

  The surface of the support may be subjected to, for example, a cutting process, a roughening process, or an alumite process for the purpose of suppressing interference fringes due to scattering of laser light.

  Between the support and the undercoat layer or photosensitive layer (charge generation layer, charge transport layer) described later, for example, for the purpose of suppressing interference fringes due to scattering of laser light, and covering scratches on the support, A conductive layer may be provided. The conductive layer is formed, for example, by applying a coating solution for a conductive layer obtained by dispersing carbon black, a conductive pigment, a resistance adjusting pigment in a solvent together with a binder resin, and drying the obtained coating film. can do. Moreover, you may add to the coating liquid for conductive layers the compound which hardens and polymerizes by heating, ultraviolet irradiation, and radiation irradiation, for example. For example, the surface of a conductive layer in which a conductive pigment or a resistance adjusting pigment is dispersed tends to be roughened.

  Examples of the binder resin used for the conductive layer include acrylic resin, allyl resin, alkyd resin, ethyl cellulose resin, ethylene-acrylic acid copolymer, epoxy resin, casein resin, silicone resin, gelatin resin, and phenol resin. In addition, a butyral resin, a polyacrylate resin, a polyacetal resin, a polyamideimide resin, a polyamide resin, a polyallyl ether resin, a polyimide resin, a polyurethane resin, a polyester resin, a polycarbonate resin, and a polyethylene resin can be given.

  In addition, polyvinyl chloride, polyvinyl acetate, polyvinyl acetal, polystyrene resin, polysulfone resin, polyvinyl alcohol resin, and polyphenylene oxide are exemplified. Examples thereof include polyvinyl fluoride, polybutadiene resin, polypropylene resin, melamine resin, urea resin, agarose resin, and cellulose resin.

  Examples of the conductive pigment and the resistance adjusting pigment include particles of metal (alloy) such as aluminum, zinc, copper, chromium, nickel, silver, and stainless steel, and those obtained by vapor deposition on the surface of plastic particles. It is also possible to use metal oxide particles such as zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin-doped indium oxide, antimony or tantalum-doped tin oxide. it can.

  These may be used alone or in combination of two or more. When two or more types are used in combination, they may be mixed, or may be in the form of a solid solution or fusion. Further, the conductive pigment and the resistance adjusting pigment can be subjected to a surface treatment. As the surface treatment agent, for example, a surfactant, a silane coupling agent, or a titanium coupling agent is used.

  Furthermore, for the purpose of light scattering, particles such as silicone resin fine particles and acrylic resin fine particles may be added. Moreover, you may contain additives, such as a leveling agent, a dispersing agent, antioxidant, a ultraviolet absorber, a plasticizer, a rectifying material.

  The thickness of the conductive layer is preferably 0.2 μm or more and 40 μm or less, more preferably 1 μm or more and 35 μm or less, and more preferably 5 μm or more and 30 μm or less.

  Between the support or conductive layer and the photosensitive layer (charge generation layer, charge transport layer), improvement of adhesion of the photosensitive layer, improvement of coating property, improvement of charge injection from the support, electrical breakdown of the photosensitive layer For the purpose of protecting the surface, an undercoat layer (intermediate layer) may be provided. The constituent material of the undercoat layer is not particularly limited as long as it satisfies the function. For example, it may be composed of a single resin or a mixture of a resin and a metal oxide.

  The undercoat layer composed of a single resin can be formed by applying an undercoat layer coating solution obtained by dissolving a resin (binder resin) in a solvent, and drying the resulting coating film. it can.

  Examples of the resin used for the undercoat layer composed of a single resin include polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, and an ethylene-acrylic acid copolymer. Further, casein, polyamide, N-methoxymethylated 6 nylon, copolymer nylon, glue and gelatin can be mentioned.

  The thickness of the undercoat layer formed of a single resin is preferably 0.05 μm or more and 7 μm or less, and more preferably 0.1 μm or more and 2 μm or less.

  The undercoat layer composed of a mixture of a resin and a metal oxide is obtained by applying a coating solution for an undercoat layer obtained by dispersing metal oxide particles in a solvent together with a binder resin. It can be formed by drying.

  The metal oxide particles contained in the undercoat layer composed of a mixture of resin and metal oxide contain at least one selected from the group consisting of titanium oxide, zinc oxide, tin oxide, zirconium oxide, and aluminum oxide. It is preferable that the particles are. Among the particles containing the above metal oxide, particles containing zinc oxide are more preferable.

  The metal oxide particles are particles in which the surface of the metal oxide particles is treated with a surface treatment agent such as a silane coupling agent in order to suppress black spot-like image defects due to charge injection from the support to the photosensitive layer side. There may be.

  Examples of the silane coupling agent include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, and (phenylaminomethyl) methyldimethoxysilane. Examples thereof include N-2- (aminoethyl) -3-aminoisobutylmethyldimethoxysilane, N-ethylaminoisobutylmethyldiethoxysilane, and N-methylaminopropylmethyldimethoxysilane.

  Moreover, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, methyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane are mentioned. Examples include 3-methacryloxypropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane.

  Examples of the resin contained in the undercoat layer composed of a mixture of resin and metal oxide include acrylic resin, allyl resin, alkyd resin, ethyl cellulose resin, ethylene-acrylic acid copolymer, epoxy resin, casein resin, and silicone resin. Is mentioned. Examples include gelatin resin, phenol resin, urethane resin, butyral resin, polyacrylate resin, polyacetal resin, polyamideimide resin, polyamide resin, polyallyl ether, polyimide resin, polyester resin, and polyethylene resin.

  In addition, polycarbonate resin, polystyrene resin, polysulfone resin, polyvinyl alcohol resin, polybutadiene resin, and polypropylene resin can be used.

  Among these, it is preferable to use a urethane resin having low hygroscopicity from the viewpoint of suppressing potential fluctuation under a high temperature and high humidity environment.

  The urethane resin suitably used for the undercoat layer composed of a mixture of a resin and a metal oxide is composed of a polymer of a composition of an isocyanate compound or a blocked isocyanate compound and a polyol resin.

  Examples of the blocked isocyanate compound include those obtained by blocking 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and diphenylmethane-4,4'-diisocyanate with a blocking agent. Examples include 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI) blocked with a blocking agent. Examples include hexamethylene diisocyanate (HDI), HDI-trimethylolpropane adduct, HDI-isocyanurate, and HDI-biuret blocked with a blocking agent.

  Examples of the blocking agent for the blocked isocyanate compound include oxime compounds such as formaldehyde oxime, acetoald oxime, methyl ethyl ketoxime, cyclohexanone oxime, acetone oxime, and methyl isobutyl ketoxime. Examples include active methylene compounds such as Meldrum's acid, dimethyl malonate, diethyl malonate, di-n-butyl malonate, ethyl acetate, and acetylacetone.

  Further, amine compounds such as diisopropylamine, diphenylaniline, aniline and carbazole, and imine compounds such as ethyleneimine and polyethyleneimine can be mentioned. Examples include acid imide compounds such as succinimide and maleic imide, and imidazole compounds such as malonate, imidazole, benzimidazole and 2-methylimidazole. Examples include triazole compounds such as 1,2,3-triazole, 1,2,4-triazole, 4-amino-1,2,4-triazole, and benzotriazole.

  Also, acid amide compounds such as acetanilide, N-methylacetamide, acetic acid amide, lactam compounds such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and urea compounds such as urea, thiourea, ethyleneurea, etc. It is done. Examples thereof include sulfites such as sodium bisulfite, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, and phenol compounds such as phenol and cresol.

  Further, pyrazole compounds such as pyrazole, 3,5-dimethylpyrazole, and 3-methylpyrazole, and alcohol compounds such as methanol, ethanol, 2-propanol, and n-butanol can be used.

  Moreover, the blocked isocyanate compound which combined 1 type (s) or 2 or more types of these blocking agents may be sufficient. Examples of the polyol resin include a polyvinyl acetal resin and a polyphenol resin.

  The content ratio between the metal oxide particles and the resin is preferably 2: 1 to 4: 1 (mass ratio) of metal oxide particles: resin from the viewpoint of electrophotographic characteristics and crack suppression.

  Examples of the dispersion method include a method using a homogenizer, an ultrasonic disperser, a ball mill, a sand mill, a roll mill, a vibration mill, an attritor, and a liquid collision type high-speed disperser.

  The undercoat layer composed of a resin and metal oxide mixture further contains organic resin particles and a leveling agent, for example, for the purpose of adjusting the surface roughness of the undercoat layer or reducing cracks in the undercoat layer. You may let them. As the organic resin particles, hydrophobic organic resin particles such as silicone particles and hydrophilic organic resin particles such as cross-linked polymethacrylate resin (PMMA) particles can be used.

  Various additives can be contained in the undercoat layer composed of a mixture of a resin and a metal oxide. Examples of the additive include metals such as aluminum powder and copper powder, and conductive substances such as carbon black. Examples thereof include electron transporting substances such as quinone compounds, fluorenone compounds, oxadiazole compounds, diphenoquinone compounds, alizarin compounds, and benzophenone compounds. Examples thereof include electron transport materials such as polycyclic condensed compounds and azo compounds. Organic metal compounds such as metal chelate compounds and silane coupling agents can be mentioned.

  When the conductive layer is provided, the thickness of the undercoat layer composed of a resin and metal oxide mixture is preferably 0.5 μm or more and 10 μm or less, and more preferably 2 μm or more and 8 μm or less. . When the conductive layer is not provided, the thickness is preferably 10 μm or more and 40 μm or less, and more preferably 15 μm or more and 25 μm or less.

  When the photosensitive layer is a laminated photosensitive layer, the charge generation layer is formed by applying a charge generation layer coating solution obtained by dispersing a charge generation material together with a binder resin and a solvent, and drying it. Can do. The coating solution for the charge generation layer may be prepared by adding only the charge generation material to the solvent and then dispersing the resin, and then adding the resin, or by adding both the charge generation material and the resin to the solvent and dispersing the preparation. Also good. The charge generation layer may be a vapor generation film of a charge generation material.

  Examples of the charge generating material used in the photosensitive layer include azo pigments, phthalocyanine pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, squarylium dyes, thiapyrylium salts, triphenylmethane dyes, and quinacridone pigments. Examples include azulenium salt pigments, cyanine dyes, anthanthrone pigments, pyranthrone pigments, xanthene dyes, quinoneimine dyes, and styryl dyes.

  These charge generation materials may be used alone or in combination of two or more. Among these, oxytitanium phthalocyanine, chlorogallium phthalocyanine, and hydroxygallium phthalocyanine are preferable from the viewpoint of sensitivity. Furthermore, among the hydroxygallium phthalocyanines, there are hydroxygallium phthalocyanine crystals having crystal forms having strong peaks at Bragg angles 2θ of 7.4 ° ± 0.3 ° and 28.2 ° ± 0.3 ° in CuKα characteristic X-ray diffraction. preferable.

  Examples of the binder resin used for the charge generation layer include polycarbonate resin, polyester resin, butyral resin, polyvinyl acetal resin, acrylic resin, vinyl acetate resin, and urea resin. Among these, a butyral resin is preferable. These may be used alone or in combination as a mixture or copolymer.

  Examples of the dispersion method include a method using a homogenizer, an ultrasonic disperser, a ball mill, a sand mill, a roll mill, and an attritor.

  The ratio of the charge generation material and the binder resin in the charge generation layer is preferably 0.3 parts by mass or more and 10 parts by mass or less of the charge generation material with respect to 1 part by mass of the binder resin. If necessary, for example, a sensitizer, a leveling agent, a dispersant, an antioxidant, an ultraviolet absorber, a plasticizer, and a rectifying material can be added to the charge generation layer. The thickness of the charge generation layer is preferably from 0.01 μm to 5 μm, and more preferably from 0.1 μm to 2 μm.

  When the photosensitive layer is a laminated photosensitive layer, a charge transport layer is formed on the charge generation layer. The charge transport layer can be formed by applying a charge transport layer coating solution obtained by dissolving a charge transport material and a binder resin in a solvent and drying it.

  Examples of the charge transport material used in the photosensitive layer include pyrene compounds, N-alkylcarbazole compounds, hydrazone compounds, N, N-dialkylaniline compounds, diphenylamine compounds, and triphenylamine compounds. Examples include triphenylmethane compounds, pyrazoline compounds, styryl compounds, stilbene compounds, and butadiene compounds. These charge transport materials may be used alone or in combination of two or more. Among these charge transport materials, a triphenylamine compound is preferable from the viewpoint of charge mobility.

  Examples of the binder resin used for the charge transport layer include acrylic resin, acrylonitrile resin, allyl resin, alkyd resin, epoxy resin, silicone resin, phenol resin, phenoxy resin, polyacrylamide resin, and polyamideimide resin. Examples include polyamide resins, polyallyl ether resins, polyarylate resins, polyimide resins, polyurethane resins, polyester resins, and polyethylene resins. Examples include polycarbonate resin, polysulfone resin, polyphenylene oxide resin, polybutadiene resin, polypropylene resin, and methacrylic resin.

  Among these, insulating resins such as polyarylate resin, polycarbonate, polyvinyl butyral, polyvinyl acetate, polyvinyl pyridine resin, polyvinyl alcohol, polyvinyl pyrrolidone, agarose resin, cellulose resin, and casein are exemplified.

  These may be used alone or in combination as a mixture or copolymer. Moreover, organic photoconductive polymers, such as poly-N-vinyl carbazole, polyvinyl anthracene, polyvinyl porene, can also be used. Further, a compound having a charge transport function introduced into the main chain or side chain of these resins to form a polymer charge transport material can also be used.

  If necessary, for example, an antioxidant, an ultraviolet absorber, a plasticizer, and a leveling agent can be added to the charge transport layer.

  The ratio of the charge transport material and the binder resin in the charge transport layer is preferably 0.3 parts by mass or more and 10 parts by mass or less of the charge transport material with respect to 1 part by mass of the binder resin.

  When the charge transport layer is a single layer, the thickness of the charge transport layer is preferably 5 μm or more and 40 μm or less, and more preferably 8 μm or more and 30 μm or less. When the charge transport layer has a laminated structure, the thickness of the charge transport layer on the support side is preferably 5 μm to 30 μm, and the thickness of the charge transport layer on the surface side is preferably 1 μm to 10 μm. preferable.

  In this example, when the charge transport layer is the surface layer of the electrophotographic photosensitive member, the charge transport layer is preferably composed of a resin having excellent wear resistance from the viewpoint of improving the durability of the electrophotographic photosensitive member. .

  For the purpose of improving the abrasion resistance and cleaning properties of the electrophotographic photoreceptor, a protective layer may be formed on the photosensitive layer or the charge transport layer to form a surface layer. The protective layer can be formed by forming a coating film of a coating liquid for protective layer obtained by dissolving a resin (binder resin) excellent in abrasion resistance in a solvent, and drying the coating film.

  Examples of the resin used for the protective layer include polyvinyl butyral resin, polyester resin, polycarbonate resin, polyamide resin, polyimide resin, and polyarylate resin. Examples include polyurethane resins, phenol resins, styrene-butadiene copolymers, styrene-acrylic acid copolymers, and styrene-acrylonitrile copolymers.

  The protective layer is formed by forming a coating film of a coating solution for the protective layer obtained by dissolving a polymerizable monomer or oligomer in a solvent, and curing (polymerizing) the coating film using a crosslinking or polymerization reaction to protect it. A layer may be formed. Examples of the polymerizable monomer or oligomer include a compound having a chain polymerizable functional group such as an acryloyloxy group and a styryl group, and a compound having a sequentially polymerizable functional group such as a hydroxyl group, an alkoxysilyl group, an isocyanate group, and an epoxy group. Is mentioned.

  Examples of the curing reaction include radical polymerization, ionic polymerization, thermal polymerization, photopolymerization, radiation polymerization (electron beam polymerization), plasma CVD method, and photo CVD method.

  Moreover, since the characteristics required for the protective layer are both the strength of the film and the charge transport capability, conductive particles and a charge transport material may be added to the protective layer coating solution. As the conductive particles, a conductive pigment used in the conductive layer can be used. As the charge transport material, the above-described charge transport materials can be used.

  Furthermore, it is more preferable to use a compound having both a charge transporting structure (preferably a hole transporting structure) and a polymerizable functional group in the same molecule from the viewpoint of achieving both the strength of the film and the charge transporting capability. From the viewpoint of maintaining electrophotographic characteristics, the polymerizable functional group is preferably an acryloyloxy group. Further, from the viewpoint of improving wear resistance, a compound having two or more polymerizable functional groups in the same molecule is preferable. In addition, a compound having both a charge transporting structure and a polymerizable functional group in the same molecule and the above-described charge transporting material, binder resin, polymerizable monomer or oligomer may be mixed and used.

  In addition, a filler can be added to the surface layer (charge transport layer or protective layer) of the electrophotographic photoreceptor to improve durability. Examples of the filler include organic resin particles such as fluorine atom-containing resin particles and acrylic resin particles, and inorganic particles such as alumina, silica, and titania.

  Additives can also be added for the purpose of improving various functions. Examples of the additive include conductive particles, an antioxidant, an ultraviolet absorber, a plasticizer, and a leveling agent.

  When the protective layer has a charge transporting capability, a protective layer that also serves as one charge transporting layer may be provided on the charge generation layer to form a surface layer.

  The thickness of the protective layer is preferably from 0.1 to 30 μm, and more preferably from 1 to 10 μm.

  When the photosensitive layer is a single-layer type photosensitive layer, the photosensitive layer is one or two of the group of the charge generation material, the charge transport material, and the binder resin used for the charge generation layer, the charge transport layer, and the protective layer. A coating solution for a single-layer type photosensitive layer obtained by dissolving at least a binder resin in a solvent is applied. And it can form by drying this.

  A polymerizable monomer or oligomer may be used as the binder resin, dissolved in a solvent and coated, and then crosslinked or polymerized. If necessary, for example, an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, an electron transporting substance, and a filler may be added.

  Examples of the solvent used in the coating solution for each layer of the single layer type photosensitive layer or the multilayer type photosensitive layer include, for example, alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, halogenated carbonization. Examples thereof include hydrogen solvents and aromatic solvents.

  Specific examples include water, methanol, ethanol, n-propanol, isopropanol, butanol, methyl cellosolve, methoxypropanol, dimethylformamide, dimethylacetamide, and dimethylsulfoxide. Examples include acetone, methyl ethyl ketone, cyclohexanone, diethyl ether, dipropyl ether, propylene glycol monomethyl ether, dioxane, methylal, and tetrahydrofuran.

  Further, methyl acetate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, chlorobenzene, dichloromethane, chloroform, trichloroethylene, tetrachloroethylene, carbon tetrachloride, benzene, toluene, xylene and tetralin can be mentioned. These solvents can be used alone or in combination of two or more.

  As a method for applying the coating liquid for each of the above layers, for example, a dip coating method (dip coating method), a spray coating method, or a spinner coating method can be used. Also, a roller coating method, a Meyer bar coating method, and a blade coating method can be used.

<Configuration of electrophotographic apparatus>
FIG. 5 shows an example of an electrophotographic image forming apparatus according to the present invention. In FIG. 5, a cylindrical electrophotographic photosensitive member 501 is rotationally driven with a predetermined peripheral speed (process speed) in the direction of an arrow about an axis 502. Around the electrophotographic photosensitive member 501, an image forming unit for forming an electrostatic latent image on the surface of the electrophotographic photosensitive member 501 is disposed.
Specifically, a charging unit (primary charging unit) 503 and an exposure unit (image exposure unit) are arranged along the rotation direction of the photoconductor 501. More specifically, the photoconductor 501 is uniformly charged to a predetermined potential (negative polarity in this example) by a charging roller that functions as a charging unit, and then functions as an exposure unit based on image information of a document. The laser (image exposure light) 504 emitted from the laser beam is received. In this way, an electrostatic latent image corresponding to target image information is formed on the surface of the electrophotographic photosensitive member 501.

  In this example, the effect is particularly great when charging means using discharge is used. The electrostatic latent image formed on the surface of the electrophotographic photosensitive member 501 is then developed (reversed development in this example) with a negatively charged toner (indeterminate toner or spherical toner) in the developing means 505 to form a toner image. It is formed. At this time, the particle diameter of the toner is preferably 3 to 10 μm.

  The toner image formed on the surface of the electrophotographic photosensitive member 501 is transferred onto a transfer material by a transfer bias from a transfer unit (transfer roller in this example) 506. At this time, the transfer material (sheet, recording material) 509 is synchronized with the rotation of the electrophotographic photoreceptor 501 between the electrophotographic photoreceptor 501 and the transfer means 506 (contact portion) from a transfer material supply means (not shown). Then, it is taken out and fed. At this time, from the viewpoint of improving transferability, a speed difference may be provided between the rotation of the electrophotographic photosensitive member 501 and the moving speed of the transfer means.

  Further, a bias voltage having a polarity opposite to the charge held in the toner is applied to the transfer means from a bias power source (not shown). Further, the transfer unit 506 performs primary transfer for transferring a toner image from the electrophotographic photosensitive member 501 to an intermediate transfer member (not shown) and transfer from the intermediate transfer member (not shown) to form an image of a secondary color or higher. A two-stage configuration including secondary transfer to be transferred to the material 509 may be used.

  The transfer material 509 on which the toner image has been transferred is separated from the surface of the electrophotographic photosensitive member, conveyed to the fixing means 508, and subjected to a fixing process of the toner image, whereby an electrophotographic apparatus is formed as an image formed product (print, copy). Printed out.

  The surface of the electrophotographic photosensitive member 501 after the transfer of the toner image has a cleaning member (in this example, a blade counter-contacted with the photosensitive member) disposed in contact with (in contact with) the surface of the electrophotographic photosensitive member 501. In step 507, the surface is cleaned by removing deposits such as transfer residual toner. Further, after being subjected to charge removal processing by pre-exposure light (not shown) from a pre-exposure means (not shown), it is repeatedly used for image formation. Note that pre-exposure is not always necessary.

Among the components selected from the image forming process equipment such as the electrophotographic photosensitive member 501, the charging unit 503, the developing unit 505, and the cleaning unit 507, a plurality of components are housed in a container and combined as a process cartridge (cartridge) PC. You may comprise. Further, the process cartridge PC can be configured to be detachable from an apparatus main body of an electrophotographic apparatus such as a copying machine or a laser beam printer.

  That is, at least the electrophotographic photosensitive member 501 and a cleaning unit 507 having a cleaning member disposed in contact with the electrophotographic photosensitive member are integrally supported, and the process cartridge PC is configured to be detachable from the main body of the electrophotographic apparatus. . The electrophotographic apparatus having the process cartridge PC and using at least pseudo halftone processing formed with dots as a method of expressing gradation can be configured.

  The exposure light 504 is reflected light or transmitted light from the original when the electrophotographic apparatus is a copying machine or a printer. Alternatively, a document is read by a sensor, or electronic data generated by an information device such as a personal computer is converted into a signal, and light emitted by, for example, scanning a laser beam or driving an LED array or a liquid crystal shutter array is performed according to this signal. It is. The image forming apparatus (electrophotographic apparatus) of the present example uses a pseudo halftone process formed of at least dots as a technique for expressing gradation in signal conversion.

  The electrophotographic image forming apparatus according to the present invention can generate a pseudo halftone process formed of dots using a dither matrix at the time of signalization. FIG. 16 is an example of a dot concentration type dither matrix. If this dither matrix is used, 256 gradations can be expressed by a dot pattern of 1200 dpi, 106 lpi, and 45 degrees. Specifically, the input multi-valued image data represented by 0 to 255 is compared with the numerical value (threshold value) in the dither matrix of FIG. 16, and if it is larger than the threshold value, black is printed (printed). For example, it is replaced with white (not printed) and converted to a binary image.

  The resolution used in recent electrophotographic apparatuses is mainly 600 dpi to 2400 dpi. In many cases, the number of lines is 106 to 212 lpi. Also, since black has high visibility, the screen angle is often set at 45 degrees where the visibility is angularly degraded. In the embodiment, an AM screening pattern is used as the pseudo halftone process, and a 45 degree square pattern of 106 lpi that can be formed even at 600 dpi and a 45 degree square pattern of 212 lpi (adjacent dot angle is 90 degrees) are used.

  In the case of a so-called tandem system in which the image forming apparatus is provided with a photoconductor and an image forming unit for each toner color, the configuration of this example may be adopted for at least one image forming station. It ’s fine. For example, in an image forming apparatus of a tandem system, a heater is installed in the photosensitive body in an image forming station that forms a black image, and the configuration of this example is not adopted in this image forming station, and toner images of other colors are used. The image forming station to be formed may be an image forming apparatus adopting the configuration of this example.

<Example>
Hereinafter, the present invention will be described in more detail with reference to specific examples. In the examples, “part” means “part by mass”. Further, the electrophotographic photoreceptor is hereinafter simply referred to as “photoreceptor”. In all the following examples, the shape of the opening of the recess formed on the surface of the electrophotographic photosensitive member is a circular shape in which the longest diameter of the opening and the shortest diameter of the opening are substantially equal.

(Production example of photoreceptor A before formation of recesses)
An aluminum cylinder having a diameter of 30.52 mm and a length of 370 mm was used as a support (cylindrical support).

Next, 100 parts of zinc oxide particles (specific surface area: 19 m ² / g, powder resistance: 4.7 × 10 ⁶ Ω · cm) as a metal oxide were stirred and mixed with 500 parts of toluene. To this, 0.8 part of a silane coupling agent (compound name: N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, trade name: KBM602, manufactured by Shin-Etsu Chemical Co., Ltd.) is added for 6 hours. Stir. Thereafter, toluene was distilled off under reduced pressure, followed by heating and drying at 130 ° C. for 6 hours to obtain surface-treated zinc oxide particles.

  Next, 15 parts of butyral resin (trade name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) and 15 parts of blocked isocyanate (trade name: Sumijoule 3175, manufactured by Sumitomo Bayern Urethane Co., Ltd.) as a polyol resin are mixed solution. Dissolved. The mixed solution is a mixture of 73.5 parts of methyl ethyl ketone and 73.5 parts of 1-butanol.

  To this solution, 80.8 parts of the surface-treated zinc oxide particles and 0.8 part of 2,3,4-trihydroxybenzophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, and this was added to a glass having a diameter of 0.8 mm. Dispersion was performed in a sand mill apparatus using beads in an atmosphere of 23 ± 3 ° C. for 3 hours. After the dispersion, the following two substances were added and stirred to prepare an undercoat layer coating solution.

・ Silicone oil (trade name: SH28PA, manufactured by Toray Dow Corning Silicone)
... 0.01 parts Crosslinked polymethyl methacrylate (PMMA) particles (trade name: TECHPOLYMERSSX-102, manufactured by Sekisui Plastics Co., Ltd., average primary particle size 2.5 μm)
... 5.6 parts This undercoat layer coating solution was dip-coated on the support, and the resulting coating film was dried at 160 ° C for 40 minutes to form an undercoat layer having a thickness of 18 µm. .

  Next, the following four substances were placed in a sand mill using glass beads having a diameter of 1 mm, dispersed for 4 hours, and then 700 parts of ethyl acetate was added to prepare a charge generation layer coating solution.

-Crystal form hydroxygallium phthalocyanine crystal (charge generating material) with strong peaks at 7.4 ° and 28.2 ° with Bragg angle 2θ ± 0.2 ° in CuKα characteristic X-ray diffraction. Calixarene compound represented by formula (A): 0.2 part

・ Polyvinyl butyral (trade name: ESREC BX-1, manufactured by Sekisui Chemical Co., Ltd.)
・ ・ ・ 10 parts ・ Cyclohexanone ・ ・ ・ 600 parts This coating solution for charge generation layer is dip-coated on the undercoat layer, and the resulting coating film is dried at 80 ° C. for 15 minutes to obtain a film thickness of 0.17 μm. The charge generation layer was formed.

  Next, a charge transport layer coating solution was prepared by dissolving the following five substances in a mixed solvent of 600 parts of mixed xylene and 200 parts of dimethoxymethane.

・ Compound represented by the following structural formula (B) (charge transporting substance) 30 parts ・ Compound represented by the following structural formula (C) (charge transporting substance) 60 parts ・ In the following structural formula (D) Compound shown: 10 parts Polycarbonate resin (trade name: Iupilon Z400, manufactured by Mitsubishi Engineering Plastics Co., Ltd., bisphenol Z type polycarbonate) ... 100 parts Polycarbonate represented by the following structural formula (E) ( Viscosity average molecular weight Mv: 20000)
... 0.02 parts

This charge transport layer coating solution was dip coated on the charge generation layer, and the resulting coating film was heated at 115 ° C. for 30 minutes.
Then, a charge generation layer having a film thickness of 18 μm was formed.

  Next, a mixed solvent of 20 parts of 1,1,2,2,3,3,4-heptafluorocyclopentane (trade name: Zeolora H, Nippon Zeon Co., Ltd.) / 20 parts of 1-propanol was added to The mixture was filtered with a filter (trade name: PF-040, manufactured by Advantech Toyo Co., Ltd.). The following three substances were added to this mixed solvent. By filtering this with a polyflon filter (trade name: PF-020, manufactured by Advantech Toyo Co., Ltd.), a coating solution for a second charge transport layer (protective layer) was prepared.

  ・ Hole transporting compound represented by the following structural formula (F): 90 parts

・ 1,1,2,2,3,3,4-heptafluorocyclopentane 70 parts ・ 1-propanol 70 parts This dip coating solution for charge transport layer is applied onto the charge transport layer The obtained coating film was dried at 50 ° C. for 6 minutes in the air. Thereafter, in nitrogen, the coating film was irradiated with an electron beam for 1.6 seconds under the conditions of an acceleration voltage of 70 kV and an absorbed dose of 8000 Gy while rotating the support (object to be irradiated) at 200 rpm.

  Subsequently, the temperature was raised from 25 ° C. to 125 ° C. over 30 seconds in nitrogen, and the coating film was heated. The oxygen concentration in the atmosphere during electron beam irradiation and subsequent heating was 15 ppm. Next, the second charge transport layer (protective layer) having a thickness of 5 μm was formed by performing a heat treatment at 100 ° C. for 30 minutes in the air.

  As described above, a photoreceptor A, which is an electrophotographic photoreceptor before forming a recess on the surface, was produced. The surface of the photoreceptor A was observed, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated for SCR1 and SCR2, which will be described later. The results are shown in Table 2.

(Production example of photoreceptor B before formation of recesses)
In the production example of photoconductor A, before forming a recess on the surface in the same manner as in the photoconductor A production example, except that an aluminum cylinder having a diameter of 84 mm and a length of 370 mm was used as the support (cylindrical support). A photoconductor B which is an electrophotographic photoconductor was prepared.

  The surface of the photoreceptor B was observed, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated for SCR1 and SCR2, which will be described later. The results are shown in Table 2.

(Production example of photoreceptor C before formation of recess)
In the same manner as in the photoconductor A production example, a conductive layer, an undercoat layer, a charge generation layer, and a charge transport layer were formed on a support. Next, a lubricant dispersion was obtained by the following procedure.

0.5 parts of a fluorine atom-containing resin (trade name: GF-300, manufactured by Toagosei Co., Ltd.) as a dispersant was dissolved in a mixed solvent as follows .
・ 1,1,2,2,3,3,4-heptafluorocyclopentane (trade name: Zeorora H, manufactured by Nippon Zeon Co., Ltd.) ・ ・ ・ 30 parts ・ 1-propanol ・ ・ ・ 30 parts 10 parts of polytetrafluoroethylene (trade name: Lubron L-2, manufactured by Daikin Industries, Ltd.) as a lubricant was added. This was put into a high-pressure disperser (trade name: Microfluidizer M-110EH, manufactured by Microfluidics, USA), and subjected to dispersion treatment four times at a pressure of 600 kgf / cm ² . This was filtered with a polyflon filter (trade name: PF-040, manufactured by Advantech Toyo Co., Ltd.) to obtain a lubricant dispersion.

  Thereafter, 90 parts of the hole transporting compound represented by the structural formula (F), 70 parts of 1,1,2,2,3,3,4-heptafluorocyclopentane, and 70 parts of 1-propanol were lubricated. It was added to the agent dispersion. By filtering this with a polyflon filter (trade name: PF-020, manufactured by Advantech Toyo Co., Ltd.), a coating solution for a second charge transport layer (protective layer) was prepared.

  The coating solution for the second charge transport layer was dip-coated on the charge transport layer, and the obtained coating film was dried at 50 ° C. for 6 minutes in the air. Thereafter, in nitrogen, the coating film was irradiated with an electron beam for 1.6 seconds under the conditions of an acceleration voltage of 70 kV and an absorbed dose of 8000 Gy while rotating the support (object to be irradiated) at 200 rpm. Subsequently, the temperature was raised from 25 ° C. to 125 ° C. over 30 seconds in nitrogen, and the coating film was heated. The oxygen concentration in the atmosphere during electron beam irradiation and subsequent heating was 15 ppm. Next, the second charge transport layer (protective layer) having a thickness of 5 μm was formed by performing a heat treatment at 100 ° C. for 30 minutes in the air.

  As described above, Photoconductor C, which is an electrophotographic photoconductor before forming a recess on the surface, was produced. The surface of the photoreceptor C was observed, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated for SCR1 and SCR2, which will be described later. The results are shown in Table 2.

(Manufacturing example of the photoreceptor D before forming the recess)
In the same manner as in the photoconductor A production example, a conductive layer, an undercoat layer, a charge generation layer, and a charge transport layer were formed on a support. Next, a coating solution for the second charge transport layer (protective layer) was prepared by the following procedure.

The following mixed liquid was put into a high-pressure disperser (trade name: Microfluidizer M-110EH, manufactured by Microfluidics), and subjected to dispersion treatment three times at a pressure of 600 kgf / cm ² .

・ Alumina particles (average particle size: 0.1 μm, trade name: LS-231, manufactured by Nippon Light Metal Co., Ltd.) ・ ・ ・ 10 parts ・ Chlorobenzene ・ ・ ・ 90 parts Filtration was performed with a Freon filter (trade name: PF-040, manufactured by Advantech Toyo Co., Ltd.) to prepare a dispersion. And
-Compound having the structure represented by the structural formula (C) ... 70 parts-Polycarbonate (trade name: Iupilon Z400, manufactured by Mitsubishi Engineering Plastics) ... 100 parts-The above dispersion liquid ... 200 Part: Monochlorobenzene: 400 parts Dimethoxymethane: By mixing 200 parts, a coating solution for the second charge transport layer (protective layer) was prepared.

  The coating solution for the second charge transport layer is spray-coated on the charge transport layer, and the obtained coating film is dried at 130 ° C. for 20 minutes to form a second charge transport layer (protective layer) having a thickness of 5 μm. did.

  As described above, a photoconductor D, which is an electrophotographic photoconductor before forming a recess on the surface, was produced. The surface of the photoreceptor D was observed, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated for SCR1 and SCR2, which will be described later. The results are shown in Table 2.

(Production example of photoconductor E)
A conductive layer, an undercoat layer, a charge generation layer, and a charge transport layer were formed on the support in the same manner as in the production example of the photoreceptor A before forming the recess. Next, a coating solution for the second charge transport layer (protective layer) was prepared by dissolving the following substances in 20.9 parts of 1-methoxy-2-propanol.

・ Acrylic polyol (trade name: JONCRYL-587, manufactured by Johnson Polymers) ・ ・ ・ 1.5 parts ・ Melamine resin (trade name: CYMEL-303, manufactured by Cytec Industries)
2.1 parts-N, N, N ', N'-tetrakis-[(4-hydroxymethyl) phenyl] -biphenyl-4,4'-diamine (THM-TBD) as a charge transport component
... 1.16 parts-N, N'-diphenyl-N, N'-di (3-hydroxyphenyl) -terphenyl-diamine (DHTER) as a charge transport component ... 1.93 parts-Acid catalyst (Trade name: Nacure 5225, manufactured by King Chemical Industries) ... 0.05 parts This coating solution for charge transport layer is dip coated on the charge transport layer and thermally cured at 140 ° C. for 40 minutes to obtain a film thickness. A 6 μm second charge transport layer (protective layer) was formed.

  The photoreceptor E was produced as described above. The surface of the photoreceptor E was observed by the above-described method, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated for SCR1 and SCR2, which will be described later. The results are shown in Table 2.

(Formation of recesses by mold pressure transfer)
In the press-fitting shape transfer processing apparatus having a configuration generally shown in FIG. 4, a mold having a convex shape was installed, and surface processing was performed on the electrophotographic photosensitive member before forming the concave portion.

  A mold having a convex shape is shown in FIG. In the embodiment, the regularly arranged mold shown in FIG. 6A and the irregularly arranged mold shown in FIG. 6B were used. In FIG. 6, Xm is the longest diameter of the convex part (the longest diameter when the convex part on the mold is viewed from above; the same applies hereinafter), and θ is the main scanning direction of exposure light in a square arrangement (horizontal direction in FIG. 6). ), H represents the height of the part. The mold was produced as follows.

  First, the arrangement of the convex portions was designed. In the following description of the layout design, the area and area ratio indicate the area and area ratio when the convex portion on the mold is viewed from above.

  FIG. 6A shows a square arrangement in which Y1 and Y2 are equally spaced. For the design of the square arrangement, a conversion method from Adobe Photoshop's gray scale to monochrome two gradations (halftone screen) was used.

  First, a gray scale having a density corresponding to the area ratio of the convex portion to be designed is created. For example, when the area ratio of the convex portion is desired to be 20%, a gray scale having a density of 20% is created. Next, in monochrome two-tone conversion, change the dot shape to a circle, set the number of lines (distance between Y1 and Y2) calculated from the longest diameter Xm and area ratio to be designed, and the angle θ and convert it to a halftone screen. did. When the resolution was insufficient, the coordinates of the arrangement were extracted from the obtained halftone screen, and the convex portions with the longest diameter Xm were rearranged. A square arrangement was created as described above.

  FIG. 6B shows an irregular arrangement by the above-described Floyd-Steinberg method. First, a gray scale having a density corresponding to the area ratio of the convex portion to be designed is created. Next, a square having the same area as that of one convex portion having the longest diameter Xm is set as a unit pixel, and binarization is performed using a distribution rule shown in FIG. Generated irregular pattern. At this time, only the first pixel was set to the density of the 255th gradation, and the calculation was started. Next, in the binarized irregular pattern, an irregular arrangement was created by arranging convex portions having the longest diameter Xm in pixels corresponding to the pattern.

  FIG. 6C shows a checker mark-like square in which square arrangement areas A in which Y1 and Y2 are equally spaced and square arrangement areas B in which Y3 and Y4 are equally spaced are arranged alternately every 500 μm square. Arrangement. Xm in the region A and Xn in the region B, Y1 (Y2) in the region A, and Y3 (Y4) in the region B were designed with different sizes.

  FIG. 6D shows a square arrangement in which the longest diameter is staggered, in which Xm is alternately replaced with Xn after the square arrangement of FIG. 6A is performed.

  Electronic data was created by adding the height H of the convex portion to the convex portion arrangement designed as described above. Although the three-dimensional shape of the convex portion can be arbitrarily selected, a circular dome shape is adopted in the embodiment. The resist is irradiated with light based on the created electronic data, creating a convex shape, creating a mold that is inverted, and subsequently electroforming nickel to create a nickel mold having a convex shape .

  Various molds were prepared by changing Xm, Xn, Y1 (Y2), Y3 (Y4), H, and θ by the above method.

  At the time of surface processing, the temperature of the electrophotographic photosensitive member and the mold is controlled so that the surface temperature of the electrophotographic photosensitive member becomes a predetermined temperature, and the electrophotographic photosensitive member and the pressure member are pressed at a desired pressure while performing electrophotography. The photoreceptor is rotated in the circumferential direction. Thereby, a concave portion was formed on the entire surface (circumferential surface) of the electrophotographic photosensitive member. As described above, an electrophotographic photosensitive member having a concave portion on the surface was prepared.

(Observation of the surface of the electrophotographic photoreceptor)
The surface of the electrophotographic photosensitive member having a concave portion on the surface is enlarged and observed with a laser microscope (manufactured by Keyence Corporation, trade name: VK-9500) with a 10 to 50 times lens, and the electrophotographic photosensitive member is as described above. The specific recessed part and flat part provided in the surface of this were determined.

  At the time of observation, adjustment was performed so that there is no inclination in the longitudinal direction of the electrophotographic photosensitive member, and the circumferential direction was focused on the apex of the arc of the electrophotographic photosensitive member. A square region having a side of 500 μm was obtained by connecting the enlarged images with an image connection application. Moreover, about the obtained result, image processing height data was selected with attached image analysis software, and the filter process was performed by the filter type median. Based on the above observation, the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined.

  In addition, the surface of the electrophotographic photosensitive member having a concave portion on the surface was observed by the same method as described above using another laser microscope (trade name: X-200, manufactured by Keyence Corporation). In this case, the same result as that obtained when the above laser microscope (manufactured by Keyence Corporation, trade name: VK-9500) was used was obtained. In the following examples, a laser microscope (manufactured by Keyence Co., Ltd., trade name: VK-9500) and a 50 × lens were used for observing an electrophotographic photosensitive member having a concave portion on the surface.

(Calculation of image quality degradation index)
The electrophotographic photosensitive member having a concave portion on the surface was observed with a CCD camera using GX-700 manufactured by Rebox Co., Ltd., and photographic data in a square region having a side of 10.84 mm was obtained. The binarization process was performed on the acquired image to acquire the coordinates of the concave portion arrangement. Next, the opening shape of the specific recesses obtained by laser microscope observation was reflected in the coordinates of the recess arrangement, and the arrangement of multiple recesses (A) was made.

  In addition, when the mold is observed using the laser microscope, and the outer peripheral shape of the convex portion of the mold matches the opening shape of the specific concave portion that was observed earlier, the convex portion arrangement used when creating the mold is used. This electronic data was taken as the arrangement (A) of a plurality of recesses.

  As the screen pattern (B), the following two were created using a conversion method from Adobe Photoshop's gray scale to monochrome 2 gradation (halftone screen).

-Square layout screen pattern 1 (SCR1) with a circular dot shape, line number 106 lpi, angle 45 °, printing rate 40%
-Square layout screen pattern 2 (SCR2) with a circular dot shape, 212 lpi line, 45 ° angle, 40% printing rate
The image quality degradation index was calculated according to the calculation method described above using the plurality of concave portion arrangements (A) and screen patterns (B) obtained above. Adobe (Photoshop) was used to create the image (C). For particle analysis, Keyence Corporation particle analysis software (GRADING ANALYSIS) VH-H1G1 was used.

(Image quality evaluation 1)
The electrophotographic photosensitive member having a concave portion on the surface is mounted on a cyan station of a modified machine of an electrophotographic apparatus (copier) (trade name: iR-ADV C7065) manufactured by Canon Inc., and evaluated as follows. It was.

  First, in a 23 ° C./50% RH environment, the charging device and the image exposure are performed so that the dark potential (Vd) of the electrophotographic photosensitive member is −700 V, the bright potential (Vl) is −200 V, and the developing potential is −540 V. The conditions of the apparatus and the developing apparatus were set.

  The dither matrix set to cyan in the electrophotographic apparatus was changed to a dither matrix having a line number of 106 lpi, an angle of 45 °, and a resolution of 1200 dpi.

A gray scale with a density of 40% was created in A4 size using Adobe Photoshop. By outputting via a printer driver, halftone 1 (HT1) composed of screen pattern 1 (SCR1) having a line number of 106 lpi, an angle of 45 °, and a printing rate of 40% was obtained. The obtained halftone 1 (HT1) was ranked by visual evaluation similar to the image quality evaluation 1.

  Halftone 1 (HT1) was ranked by visual evaluation compared to the limit sample. The limit sample is composed of 20 halftone images having different image quality degradation levels, which are output using a halftone image having no image quality degradation and an electrophotographic photosensitive member having a recess on the surface, with 20 electrophotographic device developers as subjects. Were set in comparison. The contents of the limit sample are shown below.

A: Image judged by all the subjects that the image quality has not deteriorated B: Image of whether or not the roughness is lowered by the subjects, and an image in which the judgment is divided C: Determination of whether the moire is lowered by the subjects D: The image with the highest degree among all the images judged by all the subjects to have reduced roughness. E: The image with the best degree among all the images judged by all subjects to have reduced moire. Image In this example, A to C are acceptable image quality degradation.

(Image quality evaluation 2)
In the image output of image quality evaluation 1, the dither matrix set to cyan in the electrophotographic apparatus was changed to a dither matrix having a line number of 212 lpi, an angle of 45 °, and a resolution of 1200 dpi. A gray scale with a density of 40% was created in A4 size using Adobe Photoshop. By outputting via a printer driver, halftone 2 (HT2) composed of screen pattern 2 (SCR2) having a line number of 212 lpi, an angle of 45 °, and a printing rate of 40% was obtained. The obtained halftone 2 (HT2) was ranked by visual evaluation similar to the image quality evaluation 1.

(Image quality evaluation 3)
An electrophotographic photosensitive member having a concave portion on the surface is mounted on a black station of a modified machine of an electrophotographic apparatus (copier) (trade name: iR-ADV C7065) manufactured by Canon Inc., and evaluated as follows. It was.

  First, in a 23 ° C./50% RH environment, the charging device and the image exposure are performed so that the dark potential (Vd) of the electrophotographic photosensitive member is −700 V, the bright potential (Vl) is −200 V, and the developing potential is −540 V. The conditions of the apparatus and the developing apparatus were set.

The dither matrix set to black in the electrophotographic apparatus was changed to a dither matrix having a line number of 106 lpi, an angle of 45 °, and a resolution of 1200 dpi. A gray scale with a density of 40% was created in A4 size using Adobe Photoshop. By outputting via a printer driver, halftone 3 (HT3) composed of screen pattern 1 (SCR1) having a line number of 106 lpi, an angle of 45 °, and a printing rate of 40% was obtained. The obtained halftone 3 (HT3) was ranked by visual evaluation similar to the image quality evaluation 1.

(Image quality evaluation 4)
An electrophotographic photosensitive member having a concave portion on the surface is mounted on a black station of a modified machine of an electrophotographic apparatus (copier) (trade name: iR-ADV C7065) manufactured by Canon Inc., and evaluated as follows. It was.

  First, in a 23 ° C./50% RH environment, the charging device and the image exposure are performed so that the dark potential (Vd) of the electrophotographic photosensitive member is −700 V, the bright potential (Vl) is −200 V, and the developing potential is −540 V. The conditions of the apparatus and the developing apparatus were set.

  A gray scale with a density of 40% was created in A4 size by Adobe Photoshop and output via a printer driver. Halftone 4 composed of screen pattern 2 (SCR2) with a line number of 212 lpi, an angle of 45 °, and a print rate of 40% by selecting halftone: resolution and resolution: 1200 dpi in the printer driver settings. (HT4) was obtained. The obtained halftone 4 (HT4) was ranked by visual evaluation similar to the image quality evaluation 1.

(Image flow evaluation 1)
A photoreceptor having a concave portion on the surface was mounted on a cyan station (contact charging method) of a modified machine of an electrophotographic apparatus (copier) (trade name: iR-ADV C7055) manufactured by Canon Inc.

  First, in an environment of 30 ° C./80% RH, the charging device and image exposure are performed so that the dark portion potential (Vd) of the electrophotographic photosensitive member is −700 V, the light portion potential (Vl) is −200 V, and the development potential is −540 V. The conditions of the apparatus and the developing apparatus were set. The dither matrix was changed to that used for image quality evaluation.

  Next, as shown in Table 2, a polyurethane rubber cleaning blade having a hardness of 77 ° was set so that the contact angle with respect to the surface of the electrophotographic photosensitive member was 28 ° and the contact pressure was 15 g / cm. With the heater (drum heater) for the electrophotographic photosensitive member turned off, 50000 continuous evaluation charts for images with a 5% A4 printing ratio were output in an environment of 30 ° C./80% RH.

  Subsequently, with the heater (drum heater) for the electrophotographic photosensitive member turned off, an evaluation chart for an image with a 5% A4 horizontal printing rate is output continuously in an environment of 30 ° C./80% RH. The sample was left for 3 days in a 30 ° C./80% RH environment with the power off.

  After being left for 3 days, the electrophotographic apparatus was started up, and an image of 1 dot-1 space with an A4 horizontal output resolution of 600 dpi was formed, and the image density in the vicinity of the charging device and the image reproducibility of the entire A4 were evaluated as follows. .

  A: In the vicinity of the charging device, there is no dot disturbance or scattering (that is, no image flow), and the image reproducibility is good.

  B: In the vicinity of the charging device, a slight dot disturbance is observed when magnified, but there is no scattering, and the image reproducibility is good for other portions.

  C: In the vicinity of the charging device, the dots are slightly disturbed or scattered when magnified, but the image reproducibility is good for other portions.

  D: Disturbance and scattering of dots occur in the vicinity of the charging device when magnified, but the image reproducibility is good for other portions.

  E: Whitening occurs on the image in the vicinity of the charging device, and the image reproducibility is slightly low in other portions.

(Image flow evaluation 2 to 10)
Except for the hardness and setting (contact angle and contact pressure) of the cleaning blade as shown in Table 3, the actual evaluation of the electrophotographic photosensitive member was performed in the same manner as the image flow evaluation 1 of the photosensitive member having a concave portion on the surface. went.

(Image Flow Evaluation 11-20)
A photoconductor having a concave portion on the surface was mounted on a black station (corona charging system) of a modified machine of an electrophotographic apparatus (copier) (trade name: iR-ADV C7055) manufactured by Canon Inc. Except for the hardness and setting (contact angle and contact pressure) of the cleaning blade as shown in Table 4, the actual evaluation of the electrophotographic photosensitive member was performed in the same manner as the image flow evaluation 1 of the photosensitive member having a recess on the surface. went.

(Production Example 1 of electrophotographic photosensitive member having a recess on the surface)
Using the electrophotographic photosensitive members A, B, C, and D before the formation of the recesses, the recesses are formed by mold press-contact shape transfer using the square arrangement mold shown in FIG. Photoconductors AA-1 to 40, BA-1 to 3, CA-1, and DA-1 were prepared. Table 5 shows the mold used for the pressure contact shape transfer and the surface temperature of the electrophotographic photosensitive member during surface processing.

  The surface of these electrophotographic photoreceptors was observed by the above-described method, and the depth of the specific recess, the longest diameter and area of the opening, the area of the flat portion, and the arrangement of the recess were determined. Subsequently, the image quality degradation index (f) was calculated. As the screen pattern (B), the above-described screen pattern 1 (SCR1) and screen pattern 2 (SCR2) were used. The results are shown in Table 5.

  Further, when the cross section of the vicinity of the second charge transport layer, which is the surface layer of the electrophotographic photosensitive member CA-1, was observed, as shown in FIG. 8A, not only the surface of the second charge transport layer. Also, a concave portion corresponding to the surface of the charge transport layer (interface between the charge transport layer and the second charge transport layer) was formed. A concave portion as shown in FIG. 8B was formed on the surface of the electrophotographic photosensitive member CA-1. A white line rectangle in FIG. 8B is a square region having a side of 500 μm.

(Production Example 2 of electrophotographic photosensitive member having a recess on the surface)
Using the electrophotographic photoreceptors A, B, C, and D before the formation of the recesses, the irregularly placed mold shown in FIG. 6B is used to form the recesses by mold press-fitting shape transfer, and the electrons having the recesses on the surface. Photoconductors AB-1 to 40, BB-1, CB-1, and DB-1 were prepared. Table 6 shows the mold used for the pressure contact shape transfer and the surface temperature of the electrophotographic photosensitive member during surface processing.

  These electrophotographic photosensitive members are observed in the same manner as in Production Example 1 of the electrophotographic photosensitive member having a concave portion on the surface, and the depth of the specific concave portion, the longest diameter and area of the opening portion, the area of the flat portion, and the arrangement of the concave portion The image quality degradation index (f) was calculated. The results are shown in Table 6.

(Production Example 3 of Electrophotographic Photoreceptor Having Recessed Surface)
Using the electrophotographic photosensitive member A before forming the concave portion, using the mold having the arrangement shown in FIGS. 6C and 6D, the concave portion is formed by mold pressure contact shape transfer, and the surface has the concave portion. AC-1 and AD-1 were prepared. Table 7 shows the mold used for pressure contact shape transfer and the surface temperature of the electrophotographic photosensitive member during surface processing.

  These electrophotographic photosensitive members are observed in the same manner as in Production Example 1 of the electrophotographic photosensitive member having a concave portion on the surface, and the depth of the specific concave portion, the longest diameter and area of the opening portion, the area of the flat portion, and the arrangement of the concave portion The image quality degradation index (f) was calculated. The results are shown in Table 7.

(Production Example 4 of Electrophotographic Photoreceptor Having Recessed Surface)
A conductive layer, an undercoat layer, a charge generation layer, and a charge transport layer were formed on the support in the same manner as in the production example of the photoreceptor A before forming the recess. Next, the following substances were dissolved in 20.9 parts of 1-methoxy-2-propanol to prepare a coating solution for the second charge transport layer (protective layer).

・ Acrylic polyol (trade name: JONCRYL-587, manufactured by Johnson Polymers) ・ ・ ・ 1.5 parts ・ Melamine resin (trade name: CYMEL-303, manufactured by Cytec Industries)
2.1 parts-N, N, N ', N'-tetrakis-[(4-hydroxymethyl) phenyl] -biphenyl-4,4'-diamine (THM-TBD) as a charge transport component
... 1.16 parts-N, N'-diphenyl-N, N'-di (3-hydroxyphenyl) -terphenyl-diamine (DHTER) as a charge transport component ... 1.93 parts-Acid catalyst (Trade name: Nacure 5225, manufactured by King Chemical Industries)... 0.05 part. Using the mold shown in Table 9, the shape of the mold was transferred to the surface of the coating film while keeping the surface temperature of the coating film at room temperature (25 ° C.). Next, a second charge transport layer (protective layer) having a film thickness of 6 μm was formed by thermosetting at 140 ° C. for 40 minutes.

  As described above, electrophotographic photoreceptors EA-1 and EB-1 having concave portions on the surface were produced. Tables 8 and 9 show the mold used for the pressure contact shape transfer and the surface temperature of the electrophotographic photosensitive member during surface processing.

  These electrophotographic photosensitive members are observed in the same manner as in Production Example 1 of the electrophotographic photosensitive member having a concave portion on the surface, and the depth of the specific concave portion, the longest diameter and area of the opening portion, the area of the flat portion, and the arrangement of the concave portion The image quality degradation index (f) was calculated. The results are shown in Tables 8 and 9.

In Production Examples 1 to 4 of the electrophotographic photosensitive member having a concave portion on the surface, the case where the shape (size / depth) of the concave portion formed on the surface of the photosensitive member is almost uniform will be described as an example. However, the following example is also acceptable. That is, as long as moire is not visually recognized, for example, an excessively large recess may be slightly formed due to a flare or the like during manufacture.

(Production Example 5 of electrophotographic photosensitive member having a concave portion on the surface)
A dry blasting process is performed on the photoreceptor A before forming the recesses by using a dry blasting apparatus having a configuration shown in FIG. 9 so that a plurality of dimple-shaped recesses are formed on the entire surface (peripheral surface) of the electrophotographic photoreceptor. Formed.

  In FIG. 9, reference numeral 901 denotes an injection nozzle for particles (abrasive particles) 905. Reference numeral 902 denotes a nozzle fixing jig for fixing the injection nozzle 901. Reference numeral 903 denotes an air (compressed air) introduction path. Reference numeral 904 denotes a path for guiding particles (abrasive particles) 905 stored in the container to the injection nozzle 901. Reference numeral 905 denotes particles (abrasive particles). Reference numeral 906 denotes a work support member for supporting the work 907. Reference numeral 907 denotes a work (an electrophotographic photosensitive member on which a concave portion is formed on the surface). Reference numeral 908 denotes an injection nozzle support member for supporting the injection nozzle 901. Reference numeral 909 denotes an injection nozzle fixing jig for fixing the injection nozzle 901.

As described above, an electrophotographic photosensitive member P having a concave portion on the surface was produced. The conditions for the dry blast treatment are as follows. After dry blasting, particles (abrasive particles) remaining on the peripheral surface of the workpiece were removed by blowing compressed air.

Particles (abrasive particles): spherical glass beads with an average particle size of 30 μm (trade name: UB-01L, manufactured by Union)
Air (compressed air) spraying pressure: 0.343 MPa (3.5 kgf / cm ² ) Injection nozzle moving speed: 430 mm / s (in the up and down arrow direction in FIG. 9)
・ Work rotation speed: 288 rpm (in the direction of the rotation arrow in FIG. 9)
・ Distance between discharge port of injection nozzle and workpiece: 100mm
・ Discharge angle of particles (abrasive particles): 90 °
-Supply amount of particles (abrasive particles): 200 g / min
-Number of times of blasting: one way × 2 times The electrophotographic photosensitive member P was observed in the same manner as in Production Example 1 of the electrophotographic photosensitive member having a concave portion on the surface, and the depth of the specific concave portion, the longest diameter and area of the opening portion, and The area of the flat portion and the arrangement of the concave portions were obtained, and the image quality degradation index (f) was calculated. The results are shown in Table 10.

(Examples 1-42)
The above-mentioned image quality evaluation 1 was performed on the photoreceptors AA-8 to 15, 18 to 20, 22 to 24, 28, 29, 31, 32, and 35 having concave portions on the surface. Further, the photoreceptors AB-8, 9, 12-15, 18-20, 22-24, 28, 29, 31, 32, 35, the photoreceptor AC-1, the photoreceptor AD-1, the photoreceptor CA-1, The above-described image quality evaluation 1 was performed on the photoconductor DA-1, the photoconductor CB-1, and the photoconductor DB-1. Furthermore, the evaluation shown in Table 11 among the image flow evaluations 1 to 10 was performed. The results are shown in Table 11.

From the above results, it can be said that an electrophotographic image forming apparatus satisfying the above requirements is an electrophotographic apparatus in which image flow hardly occurs and deterioration in image quality is suppressed.

(Examples 43 and 44)
The above-described image quality evaluation 3 was performed on the photoreceptors BA-1 and BB-1 having concave portions on the surface. Further, image flow evaluations 11 to 20 were performed. The results are shown in Table 12.

From the above results, it can be said that the electrophotographic image forming apparatus is an apparatus in which image flow hardly occurs and deterioration in image quality is suppressed even in the corona charging system.

(Examples 45-75)
The above-mentioned image quality evaluation 2 was performed on the photoreceptors AA-8, 9, 12-15, 18-20, and 22-24 having concave portions on the surface. Further, the photoreceptors AB-8, 9, 12-15, 18-20, 22-24, 31, 32, the photoreceptor AD-1, the photoreceptor CA-1, the photoreceptor DA-1, the photoreceptor CB-1, The above-mentioned image quality evaluation 2 was performed on the photoreceptor DB-1. Furthermore, the evaluation shown in Table 13 among the image flow evaluations 1 to 10 was performed. The results are shown in Table 13.

From the above results, it can be said that an electrophotographic image forming apparatus that satisfies the above requirements is an apparatus in which image flow hardly occurs and image quality deterioration is suppressed.

(Examples 76 and 77)
The above-mentioned image quality evaluation 4 was performed on the photoreceptors BA-1 and BB-1 having concave portions on the surface. Further, image flow evaluations 11 to 20 were performed. The results are shown in Table 14.

From the above results, it can be said that the electrophotographic image forming apparatus of this example is an apparatus in which image flow hardly occurs and deterioration in image quality is suppressed not only by the contact charging method but also by the corona charging method. .

(Comparative Examples 1-5)
The above-described image quality evaluation 1 was performed on the electrophotographic photoreceptors A to E having no concave portions on the surface. Further, image flow evaluations 2, 6, and 9 were performed. The results are shown in Table 15.

From the above results, it can be said that an electrophotographic apparatus using a photoconductor having no concave portion on the surface is an electrophotographic apparatus in which image flow is not sufficiently suppressed although image quality is not deteriorated.

(Comparative Examples 6 to 52)
The above-mentioned image quality evaluation 1 was performed on the photoreceptors AA-1 to 7, 16, 17, 21, 25 to 27, 30, 33, 34, and 36 to 40 having concave portions on the surface. Photoconductors AB-1 to 7, 10, 11, 16, 17, 21, 25 to 27, 30, 33, 34, 36 to 40, and photoconductor EA-1, photoconductor EB-1, and photoconductor P The above-described image quality evaluation 1 was performed. Furthermore, the evaluation shown in Table 16 among the image flow evaluations 1 to 10 was performed. The results are shown in Table 16.

From the above results, it can be said that an electrophotographic image forming apparatus that does not satisfy the above requirements is an apparatus that is insufficient in suppressing image flow and / or image quality degradation.

  In particular, in Comparative Examples 50 and 51, the longest diameter, depth, area, and arrangement of the openings of the specific recesses of the photoreceptors EA-1 and EB-1 satisfy the same requirements as in the examples. However, since shape transfer by a mold is performed before the coating film is cured, the area of the flat portion is small and the effect of suppressing image flow is insufficient.

  In Comparative Example 52, the area of the specific concave portion of the photoreceptor P is large and the area of the flat portion is small, so that the image flow is not sufficiently suppressed, and the arrangement of the concave portions does not satisfy the requirements of the example. The bitterness decreased.

(Comparative Examples 53 and 54)
The above-mentioned image quality evaluation 3 was performed on the photoreceptors BA-2 and 3 having concave portions on the surface. Further, image flow evaluations 13, 16, and 19 were performed. The results are shown in Table 17.

From the above results, it can be said that an electrophotographic image forming apparatus that does not satisfy the same requirements as in the embodiment is an apparatus that is insufficient in suppressing image flow and / or image quality degradation.

(Comparative Examples 55-112)
Photoconductors AA-1 to 11, 16, 17, 21, 25 to 40 having concave portions on the surface, photoconductors AB-1 to 11, 16, 17, 21, 25 to 30, 33 to 40, and photoconductor AC- 1. The above-described image quality evaluation 2 was performed on the photoconductor EA-1, the photoconductor EB-1, and the photoconductor P. Furthermore, the evaluation shown in Table 18 among the image flow evaluations 1 to 10 was performed. The results are shown in Table 18.

From the above results, it can be said that an electrophotographic image forming apparatus that does not satisfy the same requirements as in the embodiment is an apparatus that is insufficient in suppressing image flow and / or image quality degradation.

(Comparative Examples 113 and 114)
The above-described image quality evaluation 4 was performed on the photoreceptors BA-2 and 3 having concave portions on the surface. Further, image flow evaluations 13, 16, and 19 were performed. The results are shown in Table 19.

From the above results, it can be said that an electrophotographic image forming apparatus that does not satisfy the same requirements as in the embodiment is an apparatus that is insufficient in suppressing image flow and / or image quality degradation.

  Thus, if the configuration of the embodiment is adopted, the prior art is further developed, and an electrophotographic apparatus and an electrophotographic photosensitive member in which image flow is less likely to occur and image quality deterioration due to a concave portion on the surface of the electrophotographic photosensitive member is further suppressed. The body can be provided.

  According to the present invention, there are provided an image forming apparatus and an electrophotographic photosensitive member that are less likely to cause image flow and that can suppress deterioration in image quality due to a concave portion on the surface of the electrophotographic photosensitive member.

501 .. Electrophotographic photosensitive member 101.. Reference surface 102.. Second reference surface 103.. Third reference surface 104.. Recess (specific recess), 105.

Claims (8)

An electrophotographic photoreceptor comprising at least a support and a photosensitive layer formed on the support;
An image forming unit that forms an electrostatic latent image on the electrophotographic photosensitive member using at least a pseudo halftone process formed by dots as a method of expressing gradation,
A plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less are formed on the surface of the electrophotographic photoreceptor,
When one side in the surface of the electrophotographic photoconductor were arbitrarily extracted square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the flat portion contained in a portion other than the recess The total area is 80000 μm ² or more and 240000 μm ² or less,
The image forming apparatus, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.
<Calculation processing>
(1) From the screen pattern (B) generated by the pseudo halftone process formed by dots, the portion overlapping with the plurality of recesses is deleted to obtain an image (C). (2) Particles for the image (C) Analysis is performed, and the dot area average value SM and the dot area standard deviation (σ) are calculated. (3) The image quality degradation index (f) is obtained by the following equation (1).
  2. The image forming apparatus according to claim 1, wherein the electrophotographic photosensitive member has a protective layer on the photosensitive layer, and the plurality of concave portions are formed in the protective layer. An electrophotographic photoreceptor comprising at least a support and a photosensitive layer formed on the support;
As a technique for expressing gradation, an image forming unit that forms an electrostatic latent image on the electrophotographic photosensitive member using at least a pseudo halftone process formed by dots, and cleaning by contacting the electrophotographic photosensitive member An image forming apparatus having a blade,
A plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less are formed in at least a contact region with the blade on the surface of the electrophotographic photosensitive member,
When one side in the contact region is arbitrarily extract a square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the total area of the flat portion contained in a portion other than the recess 80000μm ² or more and 240,000 μm ² or less,
The image forming apparatus, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.
<Calculation processing>
(1) From the screen pattern (B) generated by the pseudo halftone process formed by dots, the portion overlapping with the plurality of recesses is deleted to obtain an image (C). (2) Particles for the image (C) Analysis is performed, and the dot area average value SM and the dot area standard deviation (σ) are calculated. (3) The image quality degradation index (f) is obtained by the following equation (1).
  4. The image forming apparatus according to claim 3, wherein the electrophotographic photosensitive member has a protective layer on the photosensitive layer, and the plurality of concave portions are formed in the protective layer. An electrophotographic photosensitive member in which an electrostatic latent image is formed using at least a pseudo halftone process formed by dots as a method of expressing gradation,
A support, and a photosensitive layer formed on the support,
On the surface of the electrophotographic photosensitive member, a plurality of recesses having a depth of 0.5 μm to 5 μm and a longest diameter of the opening of 20 μm to 80 μm are formed,
When one side in the surface of the electrophotographic photoconductor were arbitrarily extracted square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the flat portion contained in a portion other than the recess The total area is 80000 μm ² or more and 240000 μm ² or less,
The electrophotographic photoreceptor, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.
<Calculation processing>
(1) From the screen pattern (B) generated by the pseudo halftone process formed by dots, the portion overlapping with the plurality of recesses is deleted to obtain an image (C). (2) Particles for the image (C) Analysis is performed, and the dot area average value SM and the dot area standard deviation (σ) are calculated. (3) The image quality degradation index (f) is obtained by the following equation (1).
  6. The electrophotographic photoreceptor according to claim 5, further comprising a protective layer on the photosensitive layer, wherein the plurality of recesses are formed in the protective layer. An electrophotographic photosensitive member in which an electrostatic latent image is formed using at least a pseudo halftone process formed by dots as a technique for expressing gradation, and the surface thereof is cleaned by a blade,
A support, and a photosensitive layer formed on the support,
A plurality of recesses having a depth of 0.5 μm or more and 5 μm or less and a longest diameter of the opening of 20 μm or more and 80 μm or less are formed in a contact area with the blade on the surface of the electrophotographic photoreceptor.
When one side in the contact region is arbitrarily extract a square region of 500 [mu] m, in the square region, the total area of the concave portion 10000 ² more 90000Myuemu ² or less, the total area of the flat portion contained in a portion other than the recess 80000μm ² or more and 240,000 μm ² or less,
The electrophotographic photoreceptor, wherein the arrangement (A) of the plurality of recesses is an arrangement in which an image quality degradation index (f) calculated by performing the following arithmetic processing is 14% or less.
<Calculation processing>
(1) From the screen pattern (B) generated by the pseudo halftone process formed by dots, the portion overlapping with the plurality of recesses is deleted to obtain an image (C). (2) Particles for the image (C) Analysis is performed, and the dot area average value SM and the dot area standard deviation (σ) are calculated. (3) The image quality degradation index (f) is obtained by the following equation (1).
  8. The electrophotographic photosensitive member according to claim 7, further comprising a protective layer on the photosensitive layer, wherein the plurality of recesses are formed in the protective layer.